Card-type LED illumination source

ABSTRACT

An LED illumination source is disclosed. The illumination source includes a metal base substrate including a line pattern and an insulating layer including a composite material with an inorganic filler and a resin composition. LED bare chips are mounted on one surface of the metal base substrate An optical reflector with holes to surround the bare chips is provided on the surface of the metal base substrate on which the LED bare chips are mounted. Stress relaxing means is provided between the metal base substrate and the optical reflector.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. patent application Ser. No.10/374,614, filed Feb. 26, 2003 now U.S. Pat. No. 6,949,772, which was aContinuation of PCT/JP2002/008151, filed Aug. 8, 2002.

BACKGROUND OF THE INVENTION

The present invention relates to an LED (Light Emitting Diode)illumination apparatus and a card-type LED illumination source. Morespecifically, the present invention relates to an LED illuminationapparatus that uses a card-type LED illumination source on whichmultiple LEDs are mounted, and also relates to such a card-type LEDillumination source that can be used effectively in that LEDillumination apparatus.

Incandescent lamps, fluorescent lamps, high-pressure discharge lamps andother types of lamps have been used as luminaires or light sources forbillboards. Recently, an LED illumination source has been researched anddeveloped as a new type of illumination source that could potentiallyreplace these conventional light sources. An LED illumination source hasa longer life than any of those conventional light sources, which is oneof its advantageous features, and is widely expected to be anext-generation illumination source. To obtain a luminous fluxcomparable to that of an incandescent lamp or a fluorescent lamp,however, the LED illumination source needs to be an array of multipleLED elements because a single LED element has just a small luminousflux.

Hereinafter, conventional LED illumination sources will be describedwith reference to the accompanying drawings.

FIGS. 1( a) and 1(b) illustrate configurations of two conventional LEDillumination sources. FIGS. 2( a) and 2(b) illustrate cross-sectionalstructures of LEDs included in the two types of LED illuminationsources.

Each of these LED illumination sources includes a substrate 21 as shownin FIGS. 1( a) and 1(b). On the substrate 21, a number of LED bare chips22 are mounted. As used herein, the “LED bare chip” refers to an LEDthat is yet to be mounted and yet to be molded with a resin, forexample. For the sake of clarity, an LED that has already been molded soas not to expose its light emitting portion but still has not beenmounted yet will be herein referred to as an “LED element”. On thesubstrate 21 shown in FIG. 1( a), a plate 23, including multiple holes23 a to transmit the light that has been emitted from the LED bare chips22, is provided. On the other hand, on the substrate 21 shown in FIG. 1(b), a layered resin 24 that also transmits the light emitted from theLED bare chips 22 is provided. That is to say, the LED bare chips 22 arecovered with the resin 24.

In each of these LED illumination sources, the LED bare chip 22 ismounted in a bare chip state on the substrate 21 as shown in FIGS. 2( a)and 2(b). The LED bare chip 22 includes a chip substrate 31 of sapphire,SiC, GaAs or GaP, and a light emitting portion that has been formed onthe chip substrate 31. The light emitting portion is formed by stackingan n-type semiconductor layer 32 of GaN, for example, an active layer33, and a p-type semiconductor layer 34 in this order. The electrode 32a of the n-type semiconductor layer 32 and the electrode 34 a of thep-type semiconductor layer 34 are electrically connected to conductivelines 21 a on the substrate 21 by way of Au wires 41 and 42,respectively. It should be noted that this configuration of the lightemitting portion is just an illustrative one. Thus, the LED may have aquantum well, a Bragg reflector layer, or a resonant cavity structure.

In the configuration shown in FIGS. 1( a) and 2(a), the light that hasbeen emitted from the LED bare chip 22 is reflected from a reflectiveplane 23 a, which is the inner surface of a hole (or opening) 23 b ofthe plate 23, and then goes out of the element. The hole 23 b of theplate 23 is filled with the resin 24 so as to mold the LED bare chip 22and the wires 41 and 42 together. On the other hand, in theconfiguration shown in FIGS. 1( b) and 2(b), the light that has beenemitted from the LED bare chip 22 goes out of the element through themolding resin 24.

In the LED bare chip 22, when a forward bias voltage is applied betweenthe electrodes 32 a and 34 a of the n- and p-type semiconductor layers32 and 34, electrons and holes are injected into these semiconductorlayers and recombine with each other. As a result of this recombination,light is created in, and emitted from, the active layer 33. In an LEDillumination source, the light, emitted from multiple LED bare chips 22that have been mounted on the substrate, is utilized as illumination.

The LED bare chip 22 generates a lot of heat when emitting the light.The heat generated is supposed to be dissipated from the substrate 21 byway of the chip substrate 31. However, to make such an LED illuminationapparatus a commercially viable product, the following problems must besolved.

As described above, the luminous flux of each one of the LED bare chips22 is small. Accordingly, to achieve desired brightness, quite a few LEDbare chips 22 need to be arranged on the substrate 21. To avoid anexcessive increase in size of the substrate even when a great number ofLED bare chips 22 are arranged thereon, the LED bare chips 22 need to bemounted at an increased density.

Also, to increase the luminous flux of each LED bare chip 22 as much aspossible, a current to be supplied to the LED bare chip 22 (e.g., aneddy current of about 40 mA with a current density of about 444.4 mA/mm²per unit area, for example) needs to be greater than a current that issupplied for normal purposes other than illumination (e.g., about 20 mAwith a current density of about 222. 2 mA/mm² per unit area for a 0.3 mmsquare LED bare chip, for example). However, when such a great amount ofcurrent is supplied to each LED bare chip 22, an increased quantity ofheat is generated from the LED bare chip 22. As a result, thetemperature of the LED bare chip 22 (which will be herein referred to asa “bare chip temperature”) rises to reach a rather high level. Generallyspeaking, the bare chip temperature has significant effects on the lifeof the LED bare chip. More specifically, it is said that when the barechip temperature rises by 10° C., the life of an LED apparatus,including the LED bare chip 22, should be halved.

An LED is usually believed to have a long life. However, it is quite adifferent story if the LED is used for illumination purposes. What isworse, when the bare chip temperature rises with the increase in thequantity of heat generated, the luminous efficacy of the LED bare chip22 decreases unintentionally.

In view of these considerations, to realize an LED illuminationapparatus with a huge number of LED bare chips 22 mounted thereon at ahigh density, the heat dissipation performance should be improved, andthe bare chip temperature should be decreased, compared to theconventional ones. The optical efficiency also needs to be increased toutilize the light, emitted from the LED bare chips 22, as illuminationas efficiently as possible, or with the waste of the optical energyminimized.

To overcome these problems, various types of LED illumination sourceswith an array of LED bare chips thereon have been proposed. However,none of those conventional LED illumination sources has ever succeededin coping with all of those problems satisfactorily.

Hereinafter, the problems of the conventional LED illumination sourceswill be described with reference to FIGS. 1( a), 1(b), 2(a) and 2(b).Firstly, if the LEDs are kept ON continuously for a long time, thecenter portion of the substrate, having the huge number of LEDsintegrated thereon, gets more and more heated. As a result, thedifference in temperature between the center and peripheral portions ofthe LED substrate escalates with time. The configuration shown in FIGS.1( a) and 2(a) is adopted for an LED dot matrix display, for example. Inan LED display, the plate 23 works in such a manner as to increase thecontrast between the emitting and non-emitting portions of each LED.When LEDs are used for a display like this, not all of those LEDs arealways kept ON at full power. Thus, not so serious a heat generationproblem should happen in such a situation. However, when LEDs are usedto make an illumination apparatus, all of those LEDs must be kept ON fora long time, thus causing a non-negligible heat generation problem.

In the conventional examples described above, the substrate 21 and theplate 23, both made of the same resin, are combined together, and havesubstantially the same thermal expansion coefficients. However, a resinmaterial normally has a low thermal conductivity, and easily stores theheat generated. For that reason, such a resin material cannot be used soeffectively in an illumination apparatus that should always be kept ONat the maximum output power.

Also, since there is a difference in temperature between the center andperipheral portions of the substrate 21 to be combined with the plate23, a difference is also created between the thermal expansioncoefficient of the center portion and that of the peripheral portion,thus imposing a great stress in the peripheral portion of the substrate.When LEDs are used in an illumination apparatus, a stress is caused bythe heat every time the LEDs are turned ON and OFF repeatedly, whicheventually leads to disconnection of the electrodes 32 a or 34 a of theLEDs.

The substrate itself may include a portion, which is as thick as theplate 23 and which is made of a material with a thermal conductivitythat is approximately equal to the high thermal conductivity of thesubstrate material, instead of the plate 23 separately provided. Then,that substrate may include recesses to mount LED bare chips thereon.Even so, the heat-dissipating and uniform thermal distributingperformance is also limited by the thermal conductivity of the substratematerial.

Furthermore, when the above-described configuration is adopted, thesubstrate itself needs to be thick enough and the substrate to mount theLED bare chips 22 thereon cannot have a reduced thickness. For thatreason, even if the substrate material has a high thermal conductivity,the heat is still stored easily in the substrate. Accordingly, when keptenergized or ON for a long time with a great amount of current suppliedas in an illumination apparatus, the LED bare chips, mounted around thecenter of the substrate, in particular, will have noticeably increasedtemperatures, thus creating a big temperature difference between thecenter and peripheral portions of the substrate. Consequently, theproperties of the substrate material with the high thermal conductivitycannot be made full use of, and the heat dissipation problem is stillinsoluble. Furthermore, unless the recesses to be provided on thesurface of the substrate have relatively large sizes, a sufficient spacecannot be allowed to mount the LED bare chips 22 thereon and conductiveline the LED bare chips 22 by the wire bonding technique. In addition,the optical system used should have an increased size. Also, it iscurrently difficult to mount the LED bare chips 22 inside the recessesconsidering the capillary and collet sizes of bonders of various types.That is to say, to get the capillary or collet inserted into the recess,the recess and the optical system (i.e., the light outgoing region)should have increased sizes.

In the configuration shown in FIGS. 1( b) and 2(b) on the other hand,one side of the substrate 21 is covered with the molding resin 24.Accordingly, the time it takes to cure the molding resin 24 in thecenter portion of the substrate is different from the time it takes tocure the same resin 24 in the peripheral portion thereof. As a result, agreat residual stress is produced inside the resin. Furthermore, sincethe light that has been emitted from one LED bare chip 22 is absorbedinto other LED bare chips 22 (i.e., self-absorption by LEDs), thelight-extraction efficiency of the overall LED illumination sourcedecreases. Moreover, since the molding resin 24 functions as a heatstorage material, a temperature difference is created between the centerand peripheral portions of the substrate. In that case, the thermalexpansion coefficient also varies on the same substrate, thuspropagating the stress of the molding resin 24 to the peripheral portionof the substrate.

BRIEF SUMMARY OF THE INVENTION

In order to overcome the problems described above, an object of thepresent invention is to provide an LED illumination source and LEDillumination apparatus that can solve all of these problems (i.e.,increasing the density of integration and improving the heat dissipationperformance and optical efficiency) at the same time.

An LED illumination apparatus according to the present inventionincludes: at least one connector to be connected to an insertable andremovable card-type LED illumination source, which includes multipleLEDs that have been mounted on one surface of a substrate; and alighting drive circuit to be electrically connected to the card-type LEDillumination source by way of the connector.

In a preferred embodiment, the substrate is a metal base substrate. Aninsulating layer and a conductive line pattern are provided on thesurface of the metal base substrate such that the LEDs are mountedthereon.

In another preferred embodiment, the LEDs have been mounted in a barechip state on the substrate.

In another preferred embodiment, feeder terminals are provided at oneend of the surface of the substrate on which the LEDs have been mounted,and the center of a light outgoing region of the substrate, in which theLEDs mounted are located, is shifted from the center of the substrate.

In another preferred embodiment, the LED illumination apparatus includesa thermal conductor member. The thermal conductor member thermallycontacts with the back surface of the substrate, on which none of theLEDs is mounted, and receives heat from the back surface of thesubstrate.

In another preferred embodiment, the area of a contact portion betweenthe back surface of the substrate and the thermal conductor member isequal to or greater than the area of the light outgoing region of thesubstrate in which the LEDs mounted are located.

In another preferred embodiment, the illumination apparatus furtherincludes a feeder base for externally supplying electrical energy to thelighting drive circuit.

In another preferred embodiment, the feeder base is a base for a lightbulb.

In another preferred embodiment, the illumination apparatus includes ahousing, which transmits light emitted from the card-type LEDillumination source that is connected to the connector. This housing mayhave various optical properties to reflect, refract and diffuse thelight.

In another preferred embodiment, the illumination apparatus includes: areceiving portion, on/from which the card-type LED illumination sourceis fixable and removable; and stopper means for keeping the card-typeLED illumination source from dropping from the receiving portion. Thestopper means operates in such a manner as to allow a human user toremove the card-type LED illumination source from the receiving portionwith his or her fingers.

In another preferred embodiment, the surface of the substrate on whichthe LEDs have been mounted has a substantially rectangular shape. Thereceiving portion includes a guide for getting the card-type LEDillumination source slid and guided thereon. When fixed on the receivingportion, the card-type LED illumination source is supplied withelectrical power from the connector and has the back surface of thesubstrate thereof contact thermally with the receiving portion.

In another preferred embodiment, the illumination apparatus includes amovable mechanism with a fixing portion for fixing the card-type LEDillumination source onto the receiving portion. When fixed on thereceiving portion, the card-type LED illumination source is suppliedwith electrical power from the connector and has the back surface of thesubstrate thereof contact thermally with the receiving portion.

In another preferred embodiment, a thermal resistance between the backsurface of the substrate of the card-type LED illumination source, onwhich none of the LEDs is mounted, and the LEDs is 10° C./W or less.

In another preferred embodiment, the illumination apparatus includesmeans for dissipating heat from the back surface of the substrate onwhich none of the LEDs is mounted.

A card-type LED illumination source according to the present inventionincludes: a metal base substrate; and multiple LED bare chips that havebeen mounted on one surface of the metal base substrate. The card-typeLED illumination source is supported so as to be insertable into, andremovable from, an illumination apparatus that includes a connector anda lighting drive circuit. The back surface of the metal base substrate,on which none of the LED bare chips is mounted, thermally contacts witha portion of the illumination apparatus. A feeder terminal is providedon the surface of the metal base substrate on which the LED bare chipshave been mounted.

In a preferred embodiment, an optical reflector with holes to surroundthe LED bare chips is provided on the surface of the metal basesubstrate on which the LED bare chips have been mounted, and the LEDbare chips are encapsulated.

In another preferred embodiment, optical lenses are fitted with theholes of the optical reflector.

In another preferred embodiment, stress relaxing means is providedbetween the metal base substrate and the optical reflector.

In another preferred embodiment, the center of the metal base substrateis shifted from the center a light outgoing region of the metal basesubstrate in which the LED bare chips mounted are located.

In another preferred embodiment, a thermal resistance between the backsurface of the metal base substrate, on which none of the LED bare chipsis mounted, and the LED bare chips is 10° C./W or less.

In another preferred embodiment, an insulating layer and a conductiveline pattern are provided on the surface of the metal base substrate sothat the LED bare chips are mounted thereon. The insulating layer ismade of a composite material including at least an inorganic filler anda resin composition.

In another preferred embodiment, the insulating layer is white.

In another preferred embodiment, the illumination source includes atleast two conductive line pattern layers that are stacked one upon theother with an insulating layer interposed between them. The illuminationsource has a structure for conductive lineing the at least twoconductive line pattern layers together at a predetermined position ofthe insulating layer.

In another preferred embodiment, at least some of the LED bare chips areflip-chip bonded to the conductive line pattern on the metal basesubstrate.

In another preferred embodiment, a phosphor, which receives at leastsome of the light that has been emitted from the LED bare chips andwhich emits visible radiation, is provided on the metal base substrate.

An apparatus according to the present invention includes a connectorthat supplies electrical power to the card-type LED illumination sourceaccording to any of the preferred embodiments described above.

Another card-type LED illumination source according to the presentinvention includes multiple LED bare chips on a heat-dissipatingsubstrate. Each of the LED bare chips includes a light emitting portionon a chip substrate. The LED bare chips are provided on theheat-dissipating substrate such that a distance between the lightemitting portion and the heat-dissipating substrate is shorter than adistance between the chip substrate and the heat-dissipating substrate.A light outgoing facet of the chip substrate of the LED bare chipdefines a slope such that a peripheral portion thereof is less tall thana center portion thereof.

In a preferred embodiment, the LED bare chips are directly flip-chipbonded to the heat-dissipating substrate.

In another preferred embodiment, the heat-dissipating substrate is acomposite substrate.

In another preferred embodiment, an optical reflector is provided on theheat-dissipating substrate so as to surround each of the LED bare chipsand to control the direction of the light that has been emitted from theLED bare chip.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofthe invention, will be better understood when read in conjunction withthe appended drawings: For the purpose of illustrating the invention,there are shown in the drawings embodiments which are presentlypreferred. It should be understood, however, that the invention is notlimited to the precise arrangements and instrumentalities shown.

In the drawings:

FIG. 1( a) is a perspective view of a conventional LED illuminationsource and FIG. 1( b) is a perspective view of another conventional LEDillumination source.

FIG. 2( a) is a partial cross-sectional view of an LED in the LEDillumination source shown in FIG. 1( a) and FIG. 2( b) is a partialcross-sectional view of an LED in the LED illumination source shown inFIG. 1( b).

FIG. 3( a) is a perspective view illustrating a portion of a planar LEDillumination apparatus according to the present invention and FIG. 3( b)is a perspective view illustrating a light bulb type LED illuminationapparatus according to the present invention.

FIG. 4( a) is an exploded perspective view of a card-type LEDillumination source according to a specific embodiment of the presentinvention and FIG. 4( b) is a perspective view of the LED illuminationsource.

FIGS. 5( a) and 5(b) are cross-sectional views of an LED in card-typeLED illumination sources according to two specific embodiments of thepresent invention.

FIGS. 6( a) and 6(b) are equivalent circuit diagrams showing howmultiple LEDs of the card-type LED illumination source may be connectedtogether.

FIGS. 7( a) and 7(b) show to which directions light rays emitted fromLEDs go.

FIGS. 8( a) and 8(b) show the results of simulations on the luminousfluxes of two types of LEDs.

FIGS. 9( a) and 9(b) are cross-sectional views showing other exemplaryshapes of the light outgoing facet of the chip substrate of LEDs.

FIG. 10 is a cross-sectional view illustrating another exemplaryconfiguration for an LED.

FIGS. 11( a) through 11(d) are planar layouts showing exemplary shapesof a wafer bonding portion of the LED shown in FIG. 10.

FIG. 12 is an exploded perspective view illustrating another embodimentof a card-type LED illumination source according to the presentinvention.

FIG. 13 illustrates a connector that may be used for the LEDillumination source of the present invention.

FIG. 14( a) is a cross-sectional view illustrating a portion of thecard-type LED illumination source shown in FIG. 12 in which an LED isprovided, and FIG. 14( b) is a cross-sectional view illustrating anotherportion thereof in which feeder terminals are provided.

FIG. 15 is an equivalent circuit diagram showing how LEDs may beconnected together in the card-type LED illumination source shown inFIG. 12.

FIG. 16 is a block diagram showing a configuration for the lightingdrive circuit of an LED illumination apparatus to which the card-typeLED illumination source shown in FIG. 12 is inserted.

FIG. 17 is a planar layout illustrating an upper-level conductive linepattern of the card-type LED illumination source shown in FIG. 12.

FIG. 18 is a planar layout illustrating a lower-level conductive linepattern of the card-type LED illumination source shown in FIG. 12.

FIG. 19( a) is a plan view showing a conductive line pattern of aportion to be flip-chip (FC) bonded, FIG. 19( b) is a plan view showinga conductive line pattern of a portion to be wire bonded (WB bonded),FIG. 19( c) is a cross-sectional view of an FC-bonded LED bare chip, andFIG. 19( d) is a cross-sectional view of a WB-bonded LED bare chip.

FIG. 20 illustrates a light bulb type LED illumination apparatus asanother specific embodiment of an LED illumination apparatus accordingto the present invention.

FIG. 21 illustrates another light bulb type LED illumination apparatus,in which multiple card-type LED illumination sources are inserted, asstill another specific embodiment of an LED illumination apparatusaccording to the present invention.

FIG. 22 illustrates a desk lamp type LED illumination apparatus as yetanother specific embodiment of an LED illumination apparatus accordingto the present invention.

FIG. 23 illustrates another desk lamp type LED illumination apparatus,into/from which two card-type LED illumination sources are insertableand removable, as yet another specific embodiment of an LED illuminationapparatus according to the present invention.

FIG. 24 illustrates still another desk lamp type LED illuminationapparatus as yet another specific embodiment of an LED illuminationapparatus according to the present invention.

FIG. 25 illustrates a flashlight or penlight type LED illuminationapparatus as yet another specific embodiment of an LED illuminationapparatus according to the present invention.

FIG. 26 illustrates an LED illumination apparatus that can replace aconventional illumination apparatus using a straight-tube fluorescentlamp.

FIG. 27 illustrates an LED illumination apparatus, which can replace aconventional illumination apparatus using a circular-tube fluorescentlamp, as yet another specific embodiment of an LED illuminationapparatus according to the present invention.

FIG. 28 illustrates a downlight type LED illumination apparatus as yetanother specific embodiment of an LED illumination apparatus accordingto the present invention.

FIG. 29 illustrates an optical axis shifting type LED illuminationapparatus as yet another specific embodiment of an LED illuminationapparatus according to the present invention.

FIG. 30 illustrates a card-type LED illumination apparatus as yetanother specific embodiment of an LED illumination apparatus accordingto the present invention.

FIG. 31 illustrates a keychain type LED illumination apparatus as yetanother specific embodiment of an LED illumination apparatus accordingto the present invention.

DETAILED DESCRIPTION OF THE INVENTION

An LED illumination apparatus according to the present inventionincludes: a connector to be electrically connected to an insertable andremovable card-type LED illumination source; and a lighting drivecircuit to be electrically connected to the card-type LED illuminationsource by way of the connector. When the card-type LED illuminationsource is fitted in, the apparatus can radiate illumination. As will bedescribed in detail later, the card-type LED illumination source has astructure in which multiple LEDs are mounted on one surface of asubstrate (printed circuit board) with good heat dissipationperformance.

As already described for the conventional LED illumination sources, if agreat number of LED elements are mounted on a substrate at a highdensity and if a large amount of current is supplied to each of thoseLED elements, then the LED might generate an excessive quantity of heatto shorten the life of the LED potentially. This is a major problem thatconstituted a serious obstacle to popularizing LED illuminationapparatuses.

According to the present invention, the light source of an illuminationapparatus is implemented as an insertable and removable card-typestructure, thereby dissipating the heat, generated from the LEDs, muchmore smoothly. In addition, only a light source with its life ended canbe replaced with a brand-new light source. Thus, the overall structureof the LED illumination apparatus, other than the light source, can beused for a long time.

To improve the heat dissipation performance, an LED is preferablymounted as a bare chip on one surface of a substrate. This is becausethe heat generated from the LED is directly transmitted to the substrateand therefore the substrate can exhibit improved heat dissipationperformance in that case.

By integrating the LEDs and feeder terminals together on one surface, orthe principal surface, of the substrate, the other surface (i.e., backsurface) thereof, which is opposed to the principal surface, can befully used as a heat-conducting plane for heat dissipation purposes. Asa result, the area of contact between this LED illumination apparatusand a thermal conductor member can be at least equal to, or even greaterthan, the area of a light outgoing region in which the LEDs are mounted.To increase the heat conduction, the back surface of the substrate, onwhich no LEDs are mounted, is preferably made of a metal.

If the sizes of the card-type LED illumination source and the positionsof the feeder terminals are standardized, then the card-type LEDillumination source can be used in various types of illuminationapparatuses, and can be mass-produced at a reduced cost.

To ensure good electrical insulation between the feeder terminals and tostrike an adequate balance between the electrodes and other units to beassembled together, the pitch of the feeder terminals may be defined tobe 0.3 mm, 0.5 mm, 0.8 mm, 1.25 mm, 1.27 mm, 1.5 mm or 2.54 mm.Substrates for the card-type LED illumination sources are preferablymass-produced by dicing a wafer of a huge size into a great number ofsubstrates for card-type LED illumination sources. However, the dicingprocess cannot be free from manufacturing errors. In the LEDillumination apparatus, the size of the connector, into/from which thecard-type LED illumination source is inserted and removed, is alsoslightly variable during its mechanical manufacturing process.Accordingly, if the pitch between the electrodes is too small, then thefeeder terminals might be short-circuited together in the connectorportion of the LED illumination apparatus. For that reason, the pitchbetween the electrodes is preferably defined to be at least 0.8 mm.

Also, the forward voltage decreases in an LED at an elevatedtemperature. Accordingly, to increase the stability of its operation,the LED is preferably driven with a constant current supplied ratherthan a constant voltage applied. When driven with a constant currentsupplied, then the card-type LED light source needs the same number ofground lines as that of constant-current driving paths. Preferably,multiple grounded feeder terminals are provided on the substrate so asto be electrically isolated from each other. Thus, the LED illuminationapparatus to be compatible with such a card-type LED illumination sourceis also preferably provided with multiple grounded electrode connectors.When a number of feeder terminals are arranged on the card-type LEDlight source, the pitch between the electrodes is preferably 2 mm orless, more preferably 1.25 mm or less.

If illumination is provided by using the card-type LED light source andLED illumination apparatus of the present invention and by getting blue,green (or cyan), yellow (or orange), red and white LEDs drivenindependently as will be described later, two electrodes are preferablyprovided for LEDs of each color (i.e., ten electrodes in total).

The card-type LED light source of the present invention may be designedin such a manner as to be driven either with a constant voltage appliedor a constant current supplied. Alternatively, the light source may alsobe designed to be driven by way of multiple electrically isolated paths.In any case, the card-type LED light source preferably includes two ormore conductive line pattern layers, which are stacked one upon theother with an insulating layer interposed between them, and preferablyhas a structure to interconnect the two or more conductive line patternlayers together.

Where a via structure is adopted as the structure for interconnectingthe two or more conductive line pattern layers together, the diameter ofvia holes may be arbitrarily selected from the range of 100 μm to 350μm, for example. Considering a possible variation in the diameter of viaholes to be provided, the width of the feeder terminals of the card-typeLED light source is preferably two or three times as large as thediameter of the via holes, and may be 200 μm to 1,050 μm, for example.

The length of the feeder terminals is preferably defined such that theconnector of the LED illumination apparatus does not directly contactwith the via metals. For that reason, the feeder terminals preferablyhave a length of 1 mm or more, for example. To downsize the card-typeLED light source, however, the length of the feeder terminals ispreferably no greater than 5 mm.

Hereinafter, preferred embodiments of an LED illumination apparatusaccording to the present invention will be described first withreference to the accompanying drawings.

Embodiment 1

FIG. 3( a) is a perspective view illustrating a portion of an LEDillumination apparatus according to the present invention and shows aheat sink 19 in which multiple insertable/removable card-type LEDillumination sources 10 are fitted.

Each of the card-type LED illumination sources 10 is inserted to apredetermined position through a slot, which is provided on a sidesurface of the heat sink 19. The heat sink 19 thermally contacts withthe back surface of the card-type LED illumination source 10 inserted,thereby dissipating the heat away from the back surface of the substrateof the card-type LED illumination source 10.

When inserted in the heat sink 19, the card-type LED illuminationsources 10 are electrically connected to a connector (not shown), whichis provided inside the heat sink 19. The card-type LED illuminationsources 10 are further connected electrically to a lighting drivecircuit (not shown) by way of the connector. As used herein, the“connector” refers to any of various types of members or components thatcan be electrically connected to the card-type LED illumination sourcethrough an insertable/removable mechanism. Connectors with variousstructures, to/from which numerous types of memory cards, for example,are inserted or removed, are on the market. According to the presentinvention, a connector that has substantially the same structure as anyof those currently available connectors may be adopted.

An LED illumination apparatus, including such a heat sink 19 and alighting drive circuit, can easily have a reduced thickness and can beused effectively as a planar light source. Also, if any of the card-typeLED illumination sources 10 gets out of order, the non-operatingcard-type LED illumination source 10 may be removed from the heat sink19 and instead a new (i.e., normally operating or non-deteriorated)card-type LED illumination source 10 may be inserted. Then, theillumination apparatus can be used continuously.

In a preferred embodiment of the present invention, the feeder terminalsare provided on the surface of the card-type LED illumination source 10such that the card-type LED illumination source 10 can be easilyinserted or removed without using any special tool or instrument. Thus,just by connecting the card-type LED illumination source 10 to theconnector, the feeder terminals can be electrically contacted with, andconnected to, the connector. Specific preferred structures of such acard-type LED illumination source 10 will be described in detail later.

As described above, in the embodiment illustrated in FIG. 3( a), theheat sink 19 thermally contacts with the back surface of the substrateof the card-type LED illumination source 10 (i.e., the surface on whichno LEDs are mounted). Accordingly, this heat sink 19 functions as athermal conductor member to receive the heat from the back surface ofthe substrate of the card-type LED illumination source. Examples ofother preferred thermal conductor members include a heat-dissipatingsheet made of silicone grease or gel, a combination of such aheat-dissipating sheet and a heat sink, and a combination of a heat pipeand a fan. Optionally, the casing of the LED illumination apparatusitself may also be used as a thermal conductor member.

Next, FIG. 3( b) will be referred to.

The LED illumination apparatus shown in FIG. 3( b) is an illuminationapparatus that can replace a known incandescent lamp, and includes: anadapter 20 to support the card-type LED illumination source thereon inan insertable/removable state; and a transparent housing 20 a to coverthe card-type LED illumination source inserted. A lighting drive circuit(not shown) is provided inside the adapter 20. The lower portion of theadapter 20 is a feeder base (lamp base for a light bulb) (e.g., a screwbase) to externally supply electric energy to the internal lightingdrive circuit. The shape and size of this feeder base may be the same asthose of the feeder base of a normal incandescent lamp. Accordingly, theLED illumination apparatus shown in FIG. 3( b) may be used by beingfitted in any currently available electric light socket in which anincandescent lamp may be screwed. It should be noted that the screw basemay be replaced with a pin base.

In the LED illumination apparatus shown in FIG. 3( b), the adapter 20includes a slot, through which the card-type LED illumination source 10is inserted. A connector (not shown) is provided at the end of the slotto electrically connect the card-type LED illumination source 10 to thelighting drive circuit. In the embodiment illustrated in FIG. 3( b), theslot is provided for the adapter 20 so as to insert or remove thecard-type LED illumination source 10 therethrough. However, theillumination source 10 does not have to be inserted or removed in thismanner. Other preferred embodiments of a non-slotted type will bedescribed later.

As described above, the card-type LED illumination source 10 shown inFIG. 3( b) has such a structure as allowing the user to insert theillumination source 10 into, or remove it from, the connector easily.Accordingly, the illumination source 10 can also be easily removablefrom a luminaire. Since the card-type LED illumination source 10 iseasily removable in this manner, the following effects can be achieved.

Firstly, a luminaire that emits a different quantity of light can beeasily provided by substituting a card-type LED illumination source 10,on which LEDs are mounted at a different density, for the existent one.Secondly, even if any card-type LED illumination source 10 hasdeteriorated in a shorter time than expected and has almost run out ofits life as light source, only the light source section can be renewedjust by replacing the exhausted card-type LED illumination source 10 asin a normal light bulb or fluorescent lamp.

Thirdly, each of the LEDs to be mounted on the card-type LEDillumination source 10 may emit light in a color having a relatively lowcorrelated color temperature, light in a color having a relatively highcorrelated color temperature, or light in a unique color such as blue,red, green or yellow, for example. By selecting an appropriate one fromthese card-type LED illumination sources 10 and inserting it into itsassociated LED illumination apparatus, the colors of the light to beemitted from the LED illumination apparatus can be switched orcontrolled.

Furthermore, if LEDs that emit light in multiple colors (i.e., two ormore colors) are mounted on the same card-type LED illumination source10, then the colors of the light emitted from the single card-type LEDillumination source 10 can range from a color having a relatively lowcorrelated color temperature to a color having a relatively highcorrelated color temperature. In that case, if the card-type LEDillumination source 10 is a two-wavelength type for emitting light raysin just two colors, then a light source having low color renderingperformance but high optical efficiency is realized. For example, if thecorrelated color temperatures should be low, then red and cyan (orgreen) emissions are preferably combined with each other. On the otherhand, if the correlated color temperatures should be high, then blue andyellow (or orange) emissions are preferably combined with each other. Itshould be noted that if a phosphor, which is excited by a blue ray andhas a peak of emission at an intermediate wavelength between blue andred parts of the visible radiation range (e.g., YAG phosphor), is addedto a combination of blue-ray-emitting and red-ray-emitting LEDs, then ahigh-efficiency light source with a general color rendering index (CRI)of 80 or more is realized. Furthermore, if the card-type LEDillumination source 10 is a three-wavelength type for emitting lightrays in three colors, then blue, cyan (or green) and red emissions arepreferably combined with each other. And if the card-type LEDillumination source 10 is a four-wavelength type for emitting light raysin four colors, then blue, cyan (or green), yellow (or orange) and redemissions are preferably combined with each other. The four-wavelengthtype, in particular, can be a light source with high color renderingperformance, which has a general CRI of over 90. It should be noted thatthe present invention is also applicable for use even if the LED barechips to be mounted emit single-color or ultraviolet rays or if whitelight is emitted by getting a fluophor or phosphor excited by the LEDbare chips. Alternatively, the fluophor or phosphor may be included inthe substrate. Furthermore, even when blue-ray-emitting LEDs, a fluophoror phosphor to be excited by a blue ray, and red-ray-emitting LEDs arecombined together, high optical efficiency and high color renderingperformance are realized at the same time.

The card-type LED illumination source 10 described above has a squarecard shape. However, the present invention is in no way limited to thisspecific preferred embodiment. The electrodes to supply electric energy(i.e., feeder terminals) are preferably provided on the substrate of thecard-type LED illumination source 10 around the region in which the LEDsare arranged. In a more preferred embodiment, multiple feeder terminalsare arranged beside one end (one side) of the substrate. If a largenumber of feeder terminals are needed, the substrate may have arectangular shape with longer sides. In that case, the center of acluster of LEDs (i.e., the center of the light outgoing region in whichthe LEDs are arranged) shifts from that of the substrate. Then, nobending stress will be placed on the center of the light outgoing regionincluding an optical system. Thus, the illumination source can resistthe bending stress sufficiently. Also, if the corners of the rectangleare rounded, then the LED luminaire is less likely scratched by thecorners of the substrate while the user is removing the card-type LEDillumination source with fingers.

It should be noted that a portion of the substrate may include a notch,mark, recess or protrusion to indicate the insertion direction of thecard-type LED illumination source 10 clearly. Then, in fitting thecard-type LED illumination source 10 in the illumination apparatus, thecard-type LED illumination source 10 can be positioned accurately andeasily with respect to the illumination apparatus.

In the preferred embodiment described above, the feeder terminals areprovided on the card-type LED illumination source and are connected tothe connector electrodes. However, any of the following alternativeconfigurations may be adopted.

-   -   i) A face bonding type cable connector part is mounted on the        electrodes of the card-type LED illumination source such that a        feeder cable can be inserted or removed into/from the card-type        LED illumination source itself, or    -   ii) A feeder cable is directly bonded to the card-type LED light        source such that the free end of the cable, which is not bonded        to the card-type LED light source, can be inserted or removed        into/from the power supply.

When one of these alternative configurations is adopted, the feedercable is preferably a flat cable with some flexibility.

Embodiment 2

Next, specific preferred embodiments of a card-type LED illuminationsource according to the present invention will be described.

FIGS. 4( a) and 4(b) illustrate a configuration for a card-type LEDillumination source according to a second specific embodiment. Thecard-type LED illumination source of this embodiment is preferably foruse in the illumination apparatus shown in FIG. 3( a) or 3(b).

In the card-type LED illumination source of this embodiment, multipleLED bare chips 2 are mounted on one surface of a heat-dissipatingsubstrate 1 as shown in FIG. 4( a). In the example illustrated in FIG.4( a), the LED bare chips 2 are arranged in matrix, or in columns androws. However, the present invention is in no way limited to thisspecific preferred embodiment. Thus, the LED bare chips 2 may bearranged in any other arbitrary pattern.

The heat-dissipating substrate 1 with the LED bare chips 2 mountedthereon is further combined with the optical reflector 3 shown in FIG.4( a) to make the card-type LED illumination source shown in FIG. 4( b).The optical reflector 3 includes the same number of openings (or holes)3 b as that of the LED bare chips 2 that are arranged on theheat-dissipating substrate 1. Thus, the light that has been emitted fromthe LED bare chips 2 goes out through the openings 3 b of the opticalreflector 3. It should be noted that to increase the light-extractionefficiency, the openings (or holes) of the optical reflector preferablyhave varying diameters such that the light outgoing portion thereof,which is more distant from the heat-dissipating substrate, has a greaterdiameter than that of their portion closer to the heat-dissipatingsubstrate.

In this embodiment, an alumina composite substrate having a high thermalconductivity of about 3.2 W/(m·K) is used as the heat-dissipatingsubstrate 1 of the card-type LED illumination source. Theheat-dissipating substrate 1 of an alumina composite is a metal basesubstrate including a metal plate as a base with a thickness of 0.5 μmto 3.0 μm, for example, and an insulating layer provided on the metalplate. To ensure a good warpage or bend strength against the heatgenerated, the substrate preferably has a thickness of at least 0.7 mm.On the other hand, to dice the mother wafer into a number of substratesjust as intended, the substrate preferably has a thickness of at most2.0 mm. Furthermore, to improve the heat dissipation performancethereof, a thermal resistance between the back surface of the substrateof the card-type LED illumination source, on which no LED bare chips aremounted, and the LED bare chips is preferably 10° C./W or less.

Next, cross-sectional structures of the card-type LED illuminationsource will be described in detail with reference to FIGS. 5( a) and5(b). FIG. 5( a) illustrates a partial cross section of an exemplaryillumination source with a single insulating layer 1 c. On the otherhand, FIG. 5( b) illustrates a partial cross section of anotherexemplary illumination source with multiple (two in this case)insulating layers 1 c and 1 e.

As can be seen from FIGS. 5( a) and 5(b), the heat-dissipating substrate1 of this embodiment includes a metal plate 1 b and insulating layer(s)1 c (and 1 e) that has or have been bonded onto the metal plate 1 b. Theinsulating layers 1 c and 1 e are preferably made of a compositematerial including an inorganic filler and a resin composition. Thetotal thickness of the two insulating layers 1 c and 1 e may be 100 μmto 400 μm, for example. FIG. 5( b) illustrates an example in which twoinsulating layers are provided. However, the number of insulating layersmay be further increased.

The inorganic filler is preferably at least one filler that is selectedfrom the group consisting of Al₂O₃, MgO, BN, SiO₂, SiC, Si₃N₄ and AlN.To increase the fill density and the thermal conductivity, particles ofthe inorganic filler are preferably spherical. The resin composition inwhich the inorganic filler is dispersed preferably includes at least oneresin that is selected from the group consisting of epoxy resin, phenolresin and cyanate resin. Furthermore, the mixture preferably includes 70wt % to 95 wt % of inorganic filler and 5 wt % to 30 wt % of resincomposition.

The metal plate 1 b maintains the mechanical strength of theheat-dissipating substrate 1 and contributes to distributing the heat inthe heat-dissipating substrate 1 as uniformly as possible. Also, themetal plate 1 b has a flat back surface. Accordingly, when the metalplate 1 b thermally contacts with a member having good thermalconductivity (e.g., a heat sink not shown), high heat dissipationeffects are achieved.

The insulating layer 1 e on the metal plate 1 b, which is the base metalof the heat-dissipating substrate 1, may have the structure describedabove. Alternatively, a low-temperature-baked glass-ceramic substrate,having a lower thermal conductivity than the composite material, mayalso be used instead. Optionally, a ceramic substrate, an enamelsubstrate, an aluminum nitride substrate or a beryllium oxide substrate,each of which has a high thermal conductivity, may also be used as thebase, although these substrates are rather expensive. However,considering its good heat dissipation performance and mechanicalstrength, it is most preferable to use a metal plate as the base metalof the heat-dissipating substrate 1. The insulating layer to be bondedonto the metal plate may be one of the substrates mentioned above (e.g.,a ceramic substrate). In that case, the insulating substrate to bebonded to the metal plate is preferably thin and preferably has astrength high enough to be bonded there. The insulating substrate mayhave a thickness of 80 μm to 1,000 μm, for example. In this manner,multiple insulating layers, made of different materials or havingdifferent compositions, may be stacked on the base metal.

On the heat-dissipating substrate 1, conductive lines 1 a (and 1 d) areprovided and electrically isolated from the metal plate 1 b by theinsulating layer(s) 1 c (and 1 e) made of the composite material.

In the example illustrated in FIG. 5( b), the conductive lines 1 a onthe first insulating layer 1 c are electrically connected to theconductive lines 1 d on the second insulating layer 1 e by way of a viametal 1 f that is provided through the first insulating layer 1 c.

As for the heat-dissipating substrate 1 shown in FIG. 5( a), when anumber of LEDs are arranged on the same substrate to emit light rays inmultiple colors (e.g., two to four colors), a simple series-parallelconnection as shown in FIG. 6( a) or a ladder connection as shown inFIG. 6( b) is adopted for each of those colors. By adopting such aladder connection, the LEDs can be turned ON with the variation incurrent-voltage characteristic thereof minimized. Also, even if just oneLED is disconnected, all of the LEDs that are connected in series to thedisconnected LED will be turned OFF in the circuit shown in FIG. 6( a).In the circuit shown in FIG. 6( b) on the other hand, nothing but thedisconnected LED will be turned OFF. In contrast, the heat-dissipatingsubstrate 1 with the multilayer structure shown in FIG. 5( b) makes itpossible to arrange LEDs of electrically different systems adjacently toeach other as shown in FIG. 15. Thus, the presence of OFF-state LEDs orthe variation in brightness is even less perceivable in this circuitconfiguration. In addition, this structure is also advantageous inmixing LED emissions in multiple colors, and makes it possible to adoptthe ladder connection.

In this embodiment, an LED 2 in a bare chip state (i.e., LED bare chip)is directly mounted on the heat-dissipating substrate 1. As shown inFIGS. 5( a) and 5(b), this LED bare chip 2 includes a light emittingportion 15 on a chip substrate 11 of sapphire. The light emittingportion 15 has a structure in which an n-type semiconductor layer 12 ofGaN, an active layer 13 and a p-type semiconductor layer 14 are stackedone upon the other.

Unlike the conventional examples shown in FIGS. 1( a) and 1(b), the LEDbare chip 2 is mounted facedown in this embodiment, i.e., such that thelight emitting portion 15 is closer to the heat-dissipating substrate 1than the chip substrate 11 is. That is to say, the electrode 14 a of thep-type semiconductor layer 14 is directly flip-chip bonded to theconductive line 1 a on the heat-dissipating substrate 1. The electrode12 a of the n-type semiconductor layer 12 is also connected to theconductive line 1 a on the heat-dissipating substrate 1 by way of a bump16, not wire. The electrodes 12 a and 14 a may also be bonded withrespective bumps. The greater the area of the electrode 12 a or 14 a ofthe LED bare chip 2 to be metal-bonded onto the conductive lines 1 a,the greater the quantity of heat dissipated. In view of thisconsideration, the configuration of this embodiment, in which light isallowed to go out from the chip substrate 11 and a great metal contactarea can be provided under the light emitting portion 15, isadvantageous.

Considering currently available LED bare chips, a width or length ofabout 250 μm to about 350 μm and a thickness of about 90 μm to about 350μm would be practical choices as sizes of each LED bare chip 2. However,the present invention is in no way limited to these specific sizes.

If the LED bare chips 2 are flip-chip bonded to the conductive linepattern and have a width and a length of about 1 mm or more as is donein this embodiment so as to increase the quantity of light that can beextracted from a single LED bare chip 2, then the following advantagesare obtained.

When the sizes of an LED bare chip are increased to 500 μm or more, theemission produced might be intense enough near the electrodes but mightbe weak at a position far away from the electrodes due to thedistributions of resistance and current density in the p- and n-typesemiconductors that are bonded to the electrodes and fed with electricenergy, which is a problem. However, this problem can be resolved byflip-chip bonding an LED bare chip of a large size and increasing thearea of the electrodes of the LED bare chip to 50% or more of theoverall area of the element as is done in this embodiment. Thisadvantage is achieved by the unique structure of the present inventionin which the light outgoing facet of an LED bare chip is opposite to thefeeding surface thereof. It should be noted that the electrodes providedfor each LED bare chip do not have to consist of just one pair (i.e.,those provided for the p- and n-type semiconductor layers in thisembodiment) but may consist of multiple pairs. Then, the variation incurrent density inside the LED bare chip can be reduced. If thosemultiple pairs of electrodes are connected by the conventional wirebonding technique, then each wire should run a long distance to reachits destination or the wire bonding process needs to be carried out anincreased number of times.

In this embodiment, the surface of the chip substrate 11, i.e., thesurface of the substrate of the LED bare chip (or the light outgoingfacet), is not completely planar but has such a shape as decreasing theheight from its raised center portion toward its periphery (e.g., a domeshape).

In the optical reflector 3 of a metal (e.g., aluminum) on theheat-dissipating substrate 1, a reflective plane 3 a that controls thedirection of the light emitted from each LED bare chip 2 is provided soas to surround the LED bare chip 2 and the hole 3 b is provided for eachLED bare chip 2. Also, this hole 3 b is filled with a resin 4 (e.g.,epoxy, resin, silicone, or a combination thereof) to mold the LED barechip 2 with. This molding resin 4 works as a lens.

In such a structure, when a forward bias voltage is applied between theelectrodes 12 a and 14 a, the electrons injected into the n-typesemiconductor layer 12 will recombine with the holes injected into thep-type semiconductor layer 14, thereby emitting light from the activelayer 13. And this emission is utilized as illumination. Also, the lightthat has been emitted laterally in FIGS. 5( a) and 5(b) gets reflectedupward by the reflective plane 3 a of the optical reflector 3, therebyincreasing the optical efficiency.

In this embodiment, when each LED bare chip 2 emits the light, a hugequantity of heat is also generated. However, the heat generated isdirectly dissipated from the light emitting portion 15 into theheat-dissipating substrate 1. At the same time, the metallic opticalreflector 3 also contributes to distributing the heat uniformly in theheat-dissipating substrate 1, thereby preventing the heat from beingconcentrated at the center of the heat-dissipating substrate 1.

The LED bare chip 2 of this embodiment may be fabricated by thefollowing process steps, for example.

First, an n-type semiconductor layer of GaN, an active layer, and ap-type semiconductor layer of GaN are deposited and stacked in thisorder on a sapphire wafer with a diameter of about 2 inches by a CVDprocess, for example, and then electrodes 12 a and 14 a are formedthereon to prepare a semiconductor wafer. Next, the semiconductor waferprepared in this manner is subjected to sand blasting and dicing processsteps, thereby making a number of LED bare chips 2.

Specifically, fine ceramic or metal particles are propelled against thesapphire side of the semiconductor wafer, thereby forming multipleisolating grooves on the sapphire side of the wafer. Thereafter, thoseisolating grooves are further deepened by the dicing process, therebycutting the wafer into multiple LED bare chips 2. In this manner,multiple LED bare chips 2, in which the light outgoing facet of the chipsubstrate 11 is raised like a dome, are obtained. In this case, byadjusting the flow rate or flow velocity of the ceramic or metalparticles to be sprayed, the surface shape of the chip substrates 11 canbe controlled. Alternatively, two dicing blades with cutting edges indifferent shapes may be used in combination. In that case, the slopedportions may be formed first by a cutting process that uses a dicingblade with one type of cutting edge and then the wafer may be fullydivided into respective chips with a dicing blade having the other typeof cutting edge.

Unlike the conventional LED bare chip including electrodes both on thetop and bottom thereof, the flip-chip bonding structure is adopted andthe upper surface of the LED bare chip is smaller than the lower surfacethereof in this embodiment. Accordingly, there is no need to concernabout the decrease in size of the upper electrode, or damage possiblydone on it, during the machining process described above. Also, since nowires are provided on the upper surface of the LED bare chip, noradiation is interfered with by any wire. Accordingly, the distributionof the emission is not disturbed by, or the optical output power is notdecreased by, the wires.

In the example described above, a sapphire wafer is supposed to be used.Alternatively, an SiC wafer, a GaN wafer or any other wafer may also beused. The point is that the wafer to be used should transmit not onlyvisible radiation but also any other radiation emitted from the LEDs. Asanother alternative, the LED bare chip may also be packaged with aconventional through hole element (such as a bullet type element), asurface mount (SM) device or a chip type element.

Those LED bare chips 2 prepared in this manner are arranged in matrix onthe heat-dissipating substrate 1 with the electrodes 12 a and 14 athereof connected to the conductive lines 1 a on the heat-dissipatingsubstrate 1. Next, the substrate 1 is covered with the optical reflector3 and then the respective LED bare chips 2 are molded with the resin 4.It should be noted that the holes 3 b of the optical reflector 3 may befilled with the resin 4 by a printing technique. In that case, a greatnumber of resin lenses can be formed at the same time, i.e.,mass-produced effectively.

In the card-type LED illumination source of the present invention, theLED bare chips 2 are arranged with the light emitting portion 15 thereoffacing the heat-dissipating substrate 1. Accordingly, unlike theconventional examples shown in FIGS. 1( a) and 1(b), no feeding wires orno wire bonding areas are needed. Thus, the space to be provided betweenadjacent LED bare chips 2 can be narrowed, and therefore, a greaternumber of LED bare chips 2 can be integrated together. This arrangementis also effectively applicable for use to realize a color mixture byusing multiple LED bare chips 2 (or bare chips) that emit light rays inmutually different colors.

In addition, the heat generated by the light emitting portion 15 isefficiently dissipated away through the heat-dissipating substrate 1with a high thermal conductivity. In this case, the heat-generating,light emitting portion 15 of each LED bare chip 2 is directly bonded tothe heat-dissipating substrate 1. Accordingly, unlike the conventionalexamples shown in FIGS. 1( a) and 1(b) in which the heat is dissipatedby way of the chip substrate, the heat generated by the light emittingportion 15 is directly dissipated away through the heat-dissipatingsubstrate 1. Thus, excellent heat dissipation performance is ensured.Accordingly, even if a huge quantity of heat has been generated, theheat can be easily dissipated away and the unwanted increase intemperature of the LED bare chips 2 can be minimized. As a result, astrong current can be supplied to each LED bare chip 2 and a greatluminous flux can be obtained.

The refractive index of the chip substrate 11 (made of sapphire) of theLED bare chips 2 is different from that of the resin 4 (such as epoxy orsilicone resin). Due to this difference in refractive index, a portionof the light that has been emitted from the light emitting portion 15 istotally reflected from the light outgoing facet of the chip substrate11. The totally reflected light is directed toward the LED bare chip 2and cannot be used for illumination purposes. Accordingly, to utilizethe produced light effectively, it is necessary to minimize this totalreflection.

In this embodiment, the light outgoing facet of the chip substrate 11 ofeach LED bare chip 2 is molded into a dome shape, not parallel to theemission plane. In this manner, the percentage of the totally reflectedlight to the overall emission from the light emitting portion 15 isdecreased. FIG. 7( a) shows to which direction the light goes from theLED bare chip of the present invention with a domed light outgoingfacet. FIG. 7( b) shows to which direction the light goes from acomparative example with a horizontal light outgoing facet.

Specifically, if the light outgoing facet is a horizontal plane, thelight impinging onto the periphery has a large angle of incidence.Accordingly, an increased percentage of the light has an angle ofincidence that reaches a critical angle (as indicated by B in FIG. 7(b)). As a result, the total reflection easily happens. In contrast, ifthe light outgoing facet is domed, a decreased percentage of the lighthas an angle of incidence that reaches the critical angle even aroundthe periphery of the light outgoing facet. Consequently, most of theemission from the light emitting portion 15 is not totally reflected butradiated away as indicated by A in FIG. 7( a).

FIGS. 8( a) and 8(b) show respective results of simulations on theluminous flux of the emission of an LED bare chip 2 in which the lightoutgoing facet of the chip substrate 11 was molded into a dome shape(i.e., an example of the present invention) and on the luminous flux ofthe emission of an LED bare chip 2 in which the light outgoing facet ofthe chip substrate 11 was a horizontal plane (i.e., a comparativeexample). Comparing the results shown in FIGS. 8( a) and 8(b), it can beseen that the luminous flux of the upwardly directed emission, availablefor use as illumination, was greater in the example of the presentinvention than in the comparative example. That is to say, the lightcould be extracted more efficiently in the example of the presentinvention. The present inventors confirmed via actual measurements thatthe light-extraction efficiency of the example of the present inventionwas 1.6 times as high as that of the comparative example.

As described above, in the card-type LED illumination source of thepresent invention, the light outgoing facet of the chip substrate 11 isdomed. Thus, the emission can be extracted non-wastefully and can beutilized as illumination very efficiently.

In the example described above, the light outgoing facet of the chipsubstrate 11 is domed. Alternatively, the facet may have any arbitraryshape as long as the shape can minimize the total reflection (i.e., afacet which is sloped downward from the raised center portion toward theperiphery). For example, either the shape shown in FIG. 9( a), in whichcurved surfaces are formed so as to increase its width toward the lightemitting portion 15 as opposed to the example described above, or theshape shown in FIG. 9( b), in which tapered surfaces are formed so as tohave a constant tilt angle, may also be adopted.

However, if the sloped surfaces are not curved but planar or polygonal,then this effect diminishes. Accordingly, the sloped surfaces arepreferably domed because the effects achieved in that case are as if alens were included in the LED bare chip 2 itself. When the LED bare chip2 functions as a lens by itself, the emission of the LED bare chip 2 isconcentrated toward the front of the lens while the quantity of light tobe emitted through the side surfaces of the LED bare chip 2 decreases.Thus, an optical system including such an LED bare chip 2 should havedecreased stray light components. As a result, the optical efficiency ofthe overall card-type LED illumination source increases.

The above-described example relates to a blue-ray-emitting card-type LEDillumination source including the LED bare chips 2, each emitting a blueray from a structure in which GaN semiconductor layers are stacked on asapphire substrate. However, the present invention is naturallyimplementable as a card-type LED illumination source including LED barechips that emit red rays, LED bare chips that emit green rays, or LEDbare chips that emit yellow rays. The present invention is alsoapplicable for use in a white-light-emitting card-type LED illuminationsource in which these four types of LED elements coexist and whichprovides either white light or light rays in various colors bycontrolling the mixture of those light rays in four colors.

Examples of alternative embodiments include blue-ray-emitting and green(or cyan)-ray-emitting LEDs of GaN that have been provided on dissimilarchip substrates of SiC and GaN, for example. In that case, the chipsubstrates themselves have some electrical conductivity. Accordingly,instead of providing the electrodes for the n- and p-type semiconductorlayers 12 and 14 that sandwich the active layer 13 between them as shownin FIGS. 5( a) and 5(b), the chip substrate itself may function as oneof the two electrodes.

Alternatively, where LED bare chips (or elements) of AlInGaP, whichradiate yellow (or orange) and red emissions, are used, a GaP substratewith a high transmittance to the emissions in these colors is preferablyused as the chip substrate. Then, the same structure may be adopted aswell.

A similar structure may also be used if the light emitting portion of anLED bare chip of AlInGaP is wafer-bonded to a sapphire substrate with atransparent electrode or a transparent substrate of glass, for example.

Furthermore, as shown in FIG. 10, a similar structure may be adopted aswell even if the light emitting portion 15 of an AlInGaP LED bare chip(element), including a metal electrode with an optical opening, ismetal-bonded (e.g., ultrasonic-welded) to a transparent chip substrate11 such as a sapphire or glass substrate including a metal electrode 18with an optical opening. In that case, the wafer bonding portion mayhave any of various planar shapes, some of which are shown in FIGS. 11(a) through 11(d).

As for the AlInGaP LED bare chip, the metal electrode with openings onthe bare chip may be metal-bonded (or wafer-bonded) to the metalelectrode with openings on the transparent chip substrate 11 before thegrowth substrate is removed from the bare chip. In that case, theprocess step of removing the growth substrate from the LED bare chip iscarried out after the metal bonding process step has been performed. Thechip substrate 11 may be shaped either before or after the wafer bondingprocess step and either before or after the process step of removing thegrowth substrate from the LED bare chip.

Optionally, the transparent substrate may also be wafer-bonded to thelight emitting portion of the LED bare chip even with an opticallytransparent adhesive means.

In the example described above, the surface shape of the chip substrate11 is defined by the sand blasting process. Alternatively, the surfaceshape may also be defined either by a water jet process or a selectivechemical etching process. As another alternative, optical lenses havinga refractive index that is approximately equal to that of the LED chipsubstrate 11 may be bonded together. Also, as already described for theprocess step of obtaining the GaN LED bare chips by machining, thesurface shape of the chip substrate 11 may also be defined by a cuttingprocess that uses dicing blades with different cutting edges.Optionally, the bare chips to be flip-chip bonded that have beensubjected to any of these processes may be included in conventionalelements such as bullet type elements or SMDs.

The above-described structure needs no wire bonding process, andtherefore, contributes to reducing the size of the optical system andincreasing the efficiency thereof.

Even when AlInGaP LEDs are used, the area of the LED electrode, which islocated closer to the heat-dissipating substrate to mount the LED barechip thereon, is preferably increased. Then, the light directed towardthe mounting substrate can be reflected back and the light-extractionefficiency can be increased.

It should be noted that the heat-dissipating substrate 1 does not haveto be the metal base substrate such as that shown in FIG. 5( a) or 5(b)but may be a metal core substrate, for example. However, when theheat-dissipating substrate 1 is a metal base substrate, the lowersurface of the substrate is a metal and a metallic optical reflector maybe disposed on the substrate. Accordingly, the heat can be dissipatedmore effectively from both the upper and lower surfaces of thesubstrate.

Embodiment 3

Next, another specific embodiment of a card-type LED illumination sourceaccording to the present invention will be described.

First, a card-type LED illumination source according to this embodimentwill be described with reference to FIG. 12.

As shown in FIG. 12, the card-type LED illumination source of thisembodiment includes a metal plate 50, a multilayer circuit board 51, anda metallic optical reflector 52. The metal plate 50 and the multilayercircuit board 51 together define one “card-type LED illuminationsource”.

The metal plate 50 is the base metal of a heat-dissipating substrate.The metal plate 50 and the optical reflector 52 may be made of aluminum,copper, stainless steel, iron, or an alloy thereof. The materials of themetal plate 50 and optical reflector 52 may be different from eachother. Considering the thermal conductivity, copper, aluminum, iron andstainless steel are preferred in this order. On the other hand, in viewof the thermal expansion coefficient, stainless steel, iron, copper andaluminum are preferred in this order. An aluminum-based material ispreferred because such a material is easy to handle in an anticorrosionprocess, for example. On the other hand, to minimize the decrease inreliability due to the thermal expansion, a stainless steel basedmaterial is preferably used.

The back surface of the metal plate 50 is flat and can contact with aflat surface of a member with a good thermal conductivity (not shown).

If the metal plate 50 is subjected to an insulation treatment such aselectrolytic polishing, aluminization processing, electroless plating orelectrolytic deposition, even direct contact of the metal plate 50 withthe conductive line pattern will not create electrical short-circuit.

It should be noted that at least portions of the surface of the metalplate 50, which should reflect the light that has been radiated from theLED bare chips, are preferably subjected to a process to increase thereflectivity. Examples of such processes to increase the reflectivityinclude the process of increasing the reflectivity by stacking multiplematerial layers with different refractive indices and the process ofincreasing the mirror reflection of the surface of the metal plate 50.

As in the second embodiment, the multilayer circuit board 51 has atwo-layer structure including first and second insulating layers, eachof which is made of a mixture of an inorganic filler and a resincomposition. Lower-level conductive lines are provided between the firstand second insulating layers and upper-level conductive lines areprovided on the second insulating layer. The upper- and lower-levelconductive lines are electrically connected together by way of viametals that are provided through the second insulating layer.

If the holes of the optical reflector 52 are filled with an LEDencapsulating resin, then concave or convex lenses may be made of theresin. Alternatively, the holes may be filled with the resin toplanarize the surface of the optical reflector 52. However, since thearea of the optical reflector 52 is smaller than that of the multilayercircuit board 51, the optical reflector 52 may be molded with a resin inits entirety. If the optical reflector 50 is completely covered with theresin, then the LED bare chips can be encapsulated more tightly.

As shown in FIG. 13, the connector to be provided on the illuminationapparatus may include: a body 55 with a guide portion for sliding andguiding the card-type LED illumination source thereon; multipleconnector electrodes 56 to be electrically connected to the card-typeLED illumination source; a metal plate (or bottom plate) 57 with a goodthermal conductivity; and interconnecting cords 58 for connecting theconnector electrodes to a circuit such as a lighting drive circuit.

When inserted into this connector, the card-type LED illumination sourcehas its feeder terminals 54 contacted with, and connected to, theirassociated connector electrodes 56. To improve the heat dissipationperformance, when the card-type LED illumination source is inserted intothis connector, all or part of the back surface of the metal plate 50preferably contacts thermally with the metal plate 57 of the connector.

In this embodiment, the feeder terminals 54 are arranged and collectedalong just one of the four sides of the upper surface of the multilayercircuit board 51 as shown in FIG. 12. Accordingly, the card-type LEDillumination source is inserted into the connector by being pushed inthe direction indicated by the arrow A in FIG. 12.

As can be seen from FIG. 12, the size of the multilayer circuit board 51is greater than that of the optical reflector 52 by the area of theregion in which the feeder terminals 54 are provided. Accordingly, inthis embodiment, the (optical) center of the region in which the LEDbare chips 53 are arranged in matrix (i.e., light outgoing region or LEDcluster region) does not correspond with the center of the substrate.Therefore, the center of the bending stress on the card-type LEDillumination source does not correspond with the center of the brittleoptical system, thus increasing the mechanical strength. Also, since thefeeder terminals 54 are collected along one end of the substrate, theother ends of the upper surface of the multilayer circuit board 51,corresponding to the three other sides, do not have to be completelyfitted with the inside surfaces of the connector. As a result, thecard-type LED illumination source may be designed more freely in respectof the shape, for example.

By appropriately setting the size of the multilayer circuit board 51(and the metal plate 50) in the length direction (i.e., the size of itstwo sides that are parallel to the arrowed direction A), the opticalcenter may be shifted to any location arbitrarily.

The optical reflector 52 basically has the same structure as the opticalreflector 3 shown in FIG. 4( a), and has the same number of openings asthat of the LED bare chips 53 to be arranged. The openings of theoptical reflector 52 are preferably filled with resin lenses, with whichthe LED bare chips 53 are encapsulated. Thus, the LED bare chips 53 canbe connected to the multilayer circuit board 51 more tightly. If theconnection between the LED bare chips 53 and the multilayer circuitboard 51 is consolidated in this manner, then screw holes may beprovided through the card body of the card-type LED illumination sourceor portions of the edges of the card-type substrate may have screwingrecesses to screw the card-type LED illumination source onto aheat-dissipating member.

The configuration of the card-type LED illumination source of thisembodiment will be described in further detail with reference to FIGS.14( a) and 14(b). FIG. 14( a) shows an LED bare chip 53 that has beenflip-chip bonded with its active layer turned facedown. In thisembodiment, one of multiple different bonding methods is adoptedaccording to the type of each LED bare chip 53 as will be describedlater.

The LED bare chip 53 has been mounted so as to be connected to theconductive line patterns 59 of the multilayer circuit board 51 and fixedon the multilayer circuit board 51. After the LED bare chips 53 havebeen mounted on the multilayer circuit board 51, the metallic opticalreflector 52 is bonded onto the multilayer circuit board 51.

The multilayer circuit board 51 includes the two-layer conductive linepatterns 59. Specifically, the conductive line patterns 59 belonging totwo different layers are interconnected together by via metals 63. Theconductive line pattern 59 on the uppermost layer is connected to theelectrodes of the LED bare chip 53 by way of Au bumps 61. The conductiveline patterns 59 may be made of copper, nickel, aluminum or an alloymainly composed of these metals.

As described above, such a multilayer circuit board 51 includesinsulating layers, each of which is made of a mixture of a resincomposition and an inorganic filler with electrical insulating property.This mixture preferably includes a thermosetting resin. By appropriatelyselecting the types and quantities of the resin composition andinorganic filler that make up the insulating layer, the thermalconductivity, linear expansivity and dielectric constant of theinsulating layer are adjustable. The insulating layer preferably has athermal conductivity of 1 W/m·K to 10 W/m·K and is preferably white. Ifsuch a white insulating layer is adopted, then visible radiation isreflected by exposed portions of the insulating layer at a higherreflectivity and the optical efficiency is further improved.

As the inorganic filler, at least one filler is preferably selected fromthe group consisting of Al₂O₃, MgO, BN, SiO₂, SiC, Si₃N₄ and AlN withexcellent thermal conductivities. The mean particle size of theinorganic filler is preferably within the range of 0.1 μm to 100 μm.This is because if the mean particle size is out of this range, the filldensity of the filler or the heat dissipation performance of thesubstrate will decrease.

As the thermosetting resin, at least one resin is preferably selectedfrom the group consisting of epoxy resin, phenol resin and cyanateresin. This is because the electrical insulating property, mechanicalstrength and heat resistance of each of these resins cured are superiorto those of any other cured resin. If necessary, the resin compositionmay further include an additive such as coupling agent, dispersingagent, coloring agent or release agent.

A sample card-type LED illumination source was modeled by a method inwhich two sheets, each having a thickness of 160 μm and made of acomposite material of an alumina filler, were used and in which amultilayer circuit board, including two insulating layers with a totalthickness of 320 μm, was prepared and bonded onto a metal base ofaluminum. When LED bare chips were directly mounted on the two-layeredalumina composite substrate on the metal base of aluminum, the thermalresistance between the LED bare chips and the base metal measured about1° C./W.

Suppose the heat should be dissipated naturally from this sample by aheat sink in no wind condition and 64 LED bare chips with sizes of about0.3 mm square should be driven at 40 mA, which is a current twice asmuch as a rated current and which has a current density of about 444mA/mm². In that case, to maintain the temperature of the LED bare chipsat about 80° C., the heat sink needs to have a surface area of about 300cm². Also, if the LED bare chips are operated with such a large currentin a natural air cooling condition, then the thermal resistance betweenthe LED bare chips and the base metal needs to be about 10° C./W orless.

In natural air cooling, the temperature of the LED bare chips should notexceed the range of 80° C. to 120° C. This is because the resinencapsulant (i.e., epoxy or silicone resin) of the LED bare chips wouldsignificantly deteriorate thermally and optically at a temperatureexceeding that range.

If the thermal resistance is about 5° C./W or less, even a heat sinkwith a normal finite area, not the heat sink with an ideal big area,should realize sufficient heat dissipation in the natural air coolingcondition. Furthermore, if the thermal resistance is about 2° C./W toabout 1° C./W or less, even a small-sized heat sink should realizesufficient heat dissipation.

A system with a thermal resistance of 1° C./W or less is also realizableeither by reducing the thickness of the insulating layers or by usinginsulating layers of a boron-based composite material with a thermalconductivity of about 3 W/mK to about 5 W/mk instead of the aluminacomposite insulating layers with a thermal conductivity of about 2 W/mKto about 4 W/mK. In that case, similar effects are also achievable evenif the area of the heat sink is further reduced.

Furthermore, even when silica composite insulating layers with a thermalconductivity of 1 W·mK to 2.5 W·mK are used, a thermal resistancefalling within the above-specified range is also realizable by makingthe insulating layers thinner than insulating layers with a higherthermal conductivity.

Each of the conductive line patterns 59 of the multilayer circuit board51 may be defined by forming a conductive line pattern on a releasecarrier such as an organic film and then transferring the conductiveline pattern from the release carrier onto the insulating layer. Theconductive line pattern may be formed on the release carrier by bondinga metal foil (e.g., copper foil) onto the release carrier with anadhesive, for example, depositing a metal film on the metal foil by anelectrolytic or electroless plating technique, and then patterning themetal film by a chemical etching process. However, if the conductiveline pattern is made of the metal foil, the surface of the insulatinglayer is preferably roughened to increase the adhesive strength of themetal foil.

The conductive line pattern 59 may be formed by any other method. Also,the conductive line pattern 59 may be either inlaid in the insulatinglayer or adhered to the flat surface of the insulating layer. The viametals 63 to conductive line together the conductive line patterns 59belonging to mutually different layers may be formed by plating theinner surface of holes (i.e., via holes or through holes) that have beenprovided through the insulating layer or by filling the holes with aconductive resin composition.

The upper surface of the multilayer circuit board 51 with such astructure is mostly covered with the optical reflector 52 but is alsopartially exposed. The feeder terminals 54 are provided on the exposedregion on the multilayer circuit board 51. These feeder terminals 54 areelectrically connected to the lighting drive circuit of the illuminationapparatus by way of the connector, into which the card-type LEDillumination source is inserted.

An underfill (or stress relaxing layer) 60 is provided between theoptical reflector 52 and the multilayer circuit board 51. The underfill60 not only relaxes the stress to be caused by the difference in thermalexpansion coefficient between the metallic optical reflector 52 and themultilayer circuit board 51 but also ensures electrical insulationbetween the optical reflector 52 and the upper-level conductive lines onthe multilayer circuit board 51.

All of the optical reflector 3 is preferably made of a metal. Bysandwiching the insulating layers as the substrate (which will be hereinreferred to as a “substrate insulating layers”) between the substratebase metal and the metallic reflector, heat can be dissipated from bothsides of the substrate. In addition, the heat at the mounting side ofthe LEDs, heat-generating bodies, can be uniformly distributed from thecenter portion toward the peripheral portions. Secondary effects ofminimizing the warpage of the two metal plates from both sides of thesubstrate insulating layer are also expected as well.

Furthermore, if the substrate insulating layers are made of a compositematerial including a resin composition and an inorganic filler, then theelasticity of such a composite material can relax the stress to beplaced on the two metal plates. As a result, the illumination apparatusto be kept ON at an elevated temperature to supply high power can haveits reliability increased.

Also, to further relax the stress and further increase the reliability,the stress relaxing layer to be provided between the optical reflectorand the substrate insulating layers needs to be made of a material thatis different from those of the optical reflector and insulating layers.A gap may be created between the insulating layer and the opticalreflector by providing either bumps on the conductive lines on theinsulating layer or lands for bumps in addition to the conductive lines.The gap may be filled with either the underfill or the resin (i.e.,epoxy or silicone resin) to mold the LEDs. Even so, the stress may alsobe relaxed. If such stress relaxing means is provided, unintentionalturn OFF or decrease in reliability is avoidable even under a strictcondition that stress is applied due to the thermal shock of a flashingtest.

The openings of the optical reflector 52 are closed with lenses thathave been made of a molded resin 62. To improve the heat dissipationperformance, the optical reflector 52 is preferably a metal plate ofaluminum, for example. However, a plate made of any other insulatingmaterial may also be used. In that case, at least portion (preferablyall) of the inner sidewall of the openings is preferably coated with areflective film that is made of a material having a higher reflectivitythan that of the insulating plate, e.g., a metal such as Ni, Al, Pt, Agor Al or an alloy mainly composed of these metals. Then, the light thathas been emitted sideward from the LEDs is appropriately reflected bythe reflective film. As a result, the optical efficiency can beincreased.

The backing metal plate 50 does not have to be made of aluminum but mayalso be made of copper. The back surface of the metal plate 50 ispreferably flat so as to contact with a good thermal conductor providedfor the connector, for example, and thereby improve the heat dissipationperformance. However, fins or linearly embossed portions may be providedon portions of the back surface for heat dissipation purposes. In thatcase, embossed portions to engage with the fins or linearly embossedportions are preferably provided on the surface of the member that willcontact with the back surface of the metal plate 50. In theconfiguration in which the card-type LED illumination source is slid andconnected to the connector, those fins or linearly embossed portions tobe provided on the back surface of the metal plate preferably extend inthe sliding direction so as not to interfere with the sliding movement.Then, the fins or linearly embossed portions themselves function asguides and the area of contact can be increased advantageously.

To increase the thermal contact between the thermal conductor member andthe card-type LED illumination source, a mechanism for pressing thethermal conductor member onto the card-type LED illumination source ispreferably adopted. Such pressure may be applied by feeder terminalswith some elasticity. However, to obtain a sufficient pressure from suchfeeder terminals alone, the feeder terminals need to have rather strongelasticity. If a mechanical pressure to be applied to achieve electricalcontact with the feeder terminals is about 50 g to about 100 g perterminal, then pressing means for applying a stronger pressure ispreferably provided additionally. As such pressing means, an elasticmember for applying a pressure of 200 g or more to portions of thecard-type LED illumination source other than the feeder terminalsthereof may be provided. A number of such pressing means may be providedas well.

If such pressing means is provided, then the mechanical pressure to beapplied to the feeder terminals does not have to be so high. Thus, thecard-type LED illumination source can be easily inserted or removedmanually with human fingers. That is to say, after having fitted thecard-type LED illumination source into the connector of the LEDillumination apparatus, the user can press the back surface of thesubstrate of the card-type LED illumination source onto the thermalconductor member strongly with the pressing means. As a result of suchhigh pressure, the card-type LED illumination source is locked onto theLED illumination apparatus so to speak, and will not drop down from theapparatus accidentally.

FIG. 14( b) illustrates a cross section of one end of the card-type LEDillumination source that is connected to the connector. In FIG. 14( b),the connector is indicated by the dashed lines. It should be noted thatthe card-type LED illumination source shown in FIG. 14( b) isillustrated as being thinner than the counterpart shown in FIG. 14( a)for convenience sake.

As can be seen from FIG. 14( b), the feeder terminal 54 is provided onthe end of the multilayer circuit board 51 so as to be located near theconnector, and is electrically connected to the conductive line pattern59 either directly or through the via metals. The region of themultilayer circuit board 51, on which the feeder terminal 54 is located,is not covered with the optical reflector 52. Thus, the connectorelectrode 56 can easily contact with the feeder terminal 54.

The connector electrode 56 and feeder terminal 54 can be easilyconnected or disconnected electrically by inserting or removing thecard-type LED illumination source into/from the connector. If a switchthat senses the insertion or removal of the card-type LED illuminationsource is provided near the end of the connector, at which the card-typeLED illumination source arrives when inserted, such that current isblocked while no card-type LED illumination source is inserted, thensafety increases. In that case, such a switch may be provided under,beside or over the card.

In FIG. 13, the connector electrodes 56 are illustrated as being visibleexternally. However, actual connector electrodes 56 are preferablydesigned such that the user cannot lay his or her fingers on theelectrodes 56 as shown in FIG. 14( b).

In this embodiment, four types of LED bare chips, each consisting of 16LED bare chips that emit red (R), green (G), blue (B) or yellow (Y)light ray, are arranged on the same substrate. The dimensions of thesubstrate include a longer-side length of 28.5 mm, a shorter-side lengthof 23.5 mm and a thickness of 1.3 mm. The rectangular region on whichthe 64 LED bare chips are arranged has dimensions of 20 mm by 20 mm by 1mm (thickness). In this example, the region on which the LEDs arearranged (i.e., the region where the reflector is present) is about 2 cmsquare. This area of the light emitting portion is approximatelyequalized with the bulb sizes of normal low-watt small-sized light bulbs(e.g., small spherical light bulbs or mini krypton lamps) such that theLED illumination source can replace any of these existent low-watt lightbulbs. A small spherical light bulb can obtain a total luminous flux ofabout 20 lm to about 50 lm at a power of about 5 W to about 10 W. On theother hand, a mini krypton lamp can obtain a total luminous flux ofabout 250 lm to about 500 lm at a power of about 22 W to about 38 W.

According to the results of experiments the present inventors carriedout, in an embodiment in which white-light-emitting LEDs were operatedat room temperature (25° C.) in natural air cooling condition, aluminous flux of about 100 lm to about 300 lm was obtained andapproximately the same quantity of light was obtained from a lightemitting portion having sizes substantially equal to those of asmall-sized light bulb. Also, if the card-type LED illumination sourceis packaged in a casing having sizes corresponding to those of a beamlight bulb so as to have a diameter not exceeding that of a beam typedichroic halogen lamp and if the center of the light outgoing regionwith the reflector (i.e., the light emitting region) is aligned with thecenter of the optical axis of the light bulb, then the distance from thecenter of the light emitting portion to the end of the longer side ofthe substantially square card (i.e., the side on which the feederterminals are provided) is:

-   -   about 13 mm when the diameter is 35 mm;    -   about 15 mm when the diameter is 40 mm; or    -   about 23 mm when the diameter is 50 mm.

The periphery of the substrate preferably has flat portions that cancontact with the guide portions. Also, to mold the entire reflector witha resin, the periphery of the substrate preferably has regions on whichno LEDs are provided. Such regions are provided on both sides of thelight outgoing region having sizes of about 2 cm square. Each of thoseregions preferably has a width of 1 mm to 3 mm. To increase the size ofthese regions (or margins), the distance from the center of the lightemitting portion to the end facet needs to be decreased.

If the card-type LED illumination source is used either by inserting itor by placing and then pressing it and if the card-type LED illuminationsource is used both as a luminaire and as a lamp, then the feederterminals are preferably provided on just one surface of the card-typeLED illumination source to make the illumination source compatible withany of various insertion/removal methods. More preferably, the card-typeLED illumination source is disposed such that the center of the mirrorreflector (or the light outgoing region) is shifted from the geometriccenter of the substrate.

To get the heat dissipated effectively from the back surface of thesubstrate of the card-type LED illumination source, the feeder terminalsare preferably collected together on the light outgoing side of thesubstrate. Furthermore, to ensure thermal contact between the backsurface of the substrate and the thermal conductor member (i.e., theheat-dissipating means) in a broad area, the card-type LED illuminationsource is preferably pressed not only by the feeder terminals but alsoby other pressing means. To get the illumination source pressed by suchmeans, margins are preferably provided on the principal surface of thesubstrate for that purpose.

The distance from the center of the light emitting portion to the endfacet of the substrate with no feeder terminals may be shorter than thedistance from the center of the light emitting portion to the end facetwith the feeder terminals. The former distance may be equalized with thewidth of the margins to be provided on both sides of the light outgoingregion. In that case, if four card-type LED illumination sources aredensely arranged such that the two sides of each of the illuminationsources are in contact with those of two other illumination sources, thegaps between the mirror reflectors (i.e., light outgoing regions) can beequalized with each other and can be as short as possible.

In view of these considerations, the present inventors modeled a samplecard-type LED illumination source in which the distance from the centerof the light outgoing region (i.e., the center of the light emittingportion) to the end facet of the substrate (i.e., the end facet with thefeeder terminals) was about 16.5 mm and in which the distance from thecenter of the light emitting portion to the opposite end facet of thesubstrate (opposite to the feeder terminal side) was about 12 mm. Byproviding a sufficiently wide space on the side opposite to the feederterminals, via connection with the lower-level conductive line patternlayer is realized outside of the reflector (or the light outgoingregion), i.e., on the margin of the substrate. If that portion has asingle-layer structure locally, then electrical connection is alsorealized without using via metals, e.g., by wiring the upper and lowerlayers together. Conversely, the other side with the feeder terminalsmay also have such a single-layer structure locally. Also, the number oflayers provided may be further increased on just portions of thesubstrate to design conductive line jumpers more freely. In that case,the margins described above become effective spaces.

In this embodiment, the feeder terminals are designed so as to have asubstantially rectangular shape and have a width of 0.8 mm, a length of2.5 mm and a pitch of 1.25 mm (i.e., distance between the centers of twoadjacent feeder terminals) in view of mechanical errors to be causedwhen the feeder terminals are contacted with the connector electrodes orthe manufacturing errors of the via metals. To maximize the number ofindependent circuits to be provided on the substrate of the card-typeLED illumination source, the number of feeder terminals is preferably aslarge as possible. In the exemplary configuration of this embodiment, 16feeder terminals may be provided.

Where the number of anode electrodes to be provided is equalized withthat of cathode electrodes to be provided to drive the LEDs with aconstant current supplied, the feeder terminals may be allocated to theLEDs that emit blue, green (or cyan), yellow (or orange), red and whiterays and six supplementary terminals (for three paths) may be provided.

In this embodiment, to ensure a minimum insulation distance between thefeeder terminals and the metal base substrate, the distance from theedge of the feeder terminals to the end facet of the substrate isdefined to be at least 2 mm. To further increase this electricalinsulation, the gap between the feeder terminals may have athree-dimensional shape, not a planar shape. That is to say, a rib maybe formed by the insulating layer.

FIG. 15 illustrates an equivalent circuit showing how 64 LED bare chips,provided for a single card-type LED illumination source, may beinterconnected together. In FIG. 15, R (+) denotes the anode side ofred-ray-emitting LED bare chips while R (−) denotes the cathode side ofthe red-ray-emitting LED bare chips. The same statement is applicable tothe other colors (Y, G and B).

FIG. 16 is a block diagram showing an exemplary configuration for an LEDlighting drive circuit. In the exemplary configuration shown in FIG. 16,the lighting drive circuit 70 of a card-type LED illumination sourceincludes a rectifying and smoothing circuit 71, a voltage step-downcircuit 72 and constant current circuits 73. The rectifying andsmoothing circuit 71 is a known circuit, which is connected to an ACpower supply of 100 V and which converts an alternating current into adirect current. It should be noted that the power supply does not haveto be AC 100 V but may be a DC power supply. When a DC power supply isadopted, the rectifying and smoothing circuit 71, which is a combinationof a smoothing circuit and voltage step-down circuit, may be replacedwith a voltage transformer (i.e., voltage step-down and step-uptransformer).

The voltage step-down circuit 72 decreases the DC voltage to anappropriate voltage to make the LEDs emit light (e.g., 18 V). Theconstant current circuits 73 include blue, green, yellow and red LEDcontrolling constant current circuits. Each of these LED controllingconstant current circuits adjusts the current to be supplied to a groupof LEDs 76 in its associated color in the card-type LED illuminationsource 75 to a constant value. The constant current circuits 73 may beelectrically connected to the groups of LEDs 76 by fitting the card-typeLED illumination source 75 in the connector of the illuminationapparatus. More specifically, the electrical continuity is realized bybringing the feeder terminals, provided on the substrate of thecard-type LED illumination source 75, into contact with their associatedfeeder terminals inside the connector.

Such a lighting drive circuit 70 includes an electrolytic capacitor as acircuit component thereof. If the temperature of the electrolyticcapacitor reaches about 100° C., its life shortens significantly. Forthat reason, the temperature near the electrolytic capacitor should besufficiently lower than 100° C. In this embodiment, the heat generatedin the card-type LED illumination source 75 is dissipated by theheat-dissipating means by way of the metal plate of the card-type LEDillumination source 75 and then the heat-dissipating member of theillumination apparatus. Accordingly, the temperature near theelectrolytic capacitor of the lighting drive circuit is maintained atabout 80° C. or less. As a result, the life of the lighting drivecircuit can also be extended.

In this embodiment, the groups of LEDs 76 for the colors blue, green (orcyan), yellow (or orange) and red are driven with a constant currentsupplied thereto, and therefore, applied with a ground potentialseparately. Accordingly, the number of feeder terminals to be providedfor the card-type LED illumination source 75 of this embodiment iseight. Half of the eight feeder terminals function as anode electrodeswhile the other half functions as cathode electrodes.

Hereinafter, multilevel conductive line patterns for the card-type LEDillumination source of this embodiment will be described with referenceto FIGS. 17 and 18. Specifically, FIG. 17 illustrates a layout for theupper-level conductive line pattern of the multilayer circuit board,while FIG. 18 illustrates a layout for the lower-level conductive linepattern thereof.

In FIGS. 17 and 18, small circular regions 79 shown on the conductivelines 78 indicate the locations of the via metals to interconnect theupper- and lower-level conductive line patterns together. In FIGS. 17and 18, the reference numerals 78 and 79 each identify just one memberfor the sake of simplicity. However, it should be naturally understoodthat a large number of conductive lines and a large number of via metalsare actually provided.

The LED bare chips are mounted on regions 85 a and 85 b, for example,which are indicated as representative ones by the dashed lines in FIG.17. FIGS. 19( a) and 19(b) respectively show the regions 85 a and 85 bon a larger scale. On the portion shown in FIG. 19( a), the LED barechip is flip-chip (FC) bonded. On the portion shown in FIG. 19( b) onthe other hand, the LED bare chip is wire-bonded (WB bonded). FIG. 19(c) shows a cross section of the FC-bonded LED bare chip, while FIG. 19(d) shows a cross section of the WB-bonded LED bare chip.

In this embodiment, the LED bare chips to emit blue or green (or cyan)light are FC bonded and the LED bare chips to emit yellow (or orange) orred light are WB bonded.

In an LED bare chip (or element) to emit the red or yellow (or orange)light (i.e., light with a relatively long wavelength), its multilayerstructure, including a light-emitting layer, is normally formed on aGaAs substrate. The GaAs substrate cannot transmit the red or yellowlight easily, and therefore, is disposed under the light-emitting layer.Accordingly, such an LED bare chip cannot be bonded facedown.

In the FC bonded structure shown in FIG. 19( c) on the other hand, n andp electrodes are disposed so as to face the light-emitting layer of theLED bare chip, and are connected to the conductive lines (i.e., theupper-level conductive lines) on the multilayer circuit board by way ofAu bumps.

In this embodiment, the conductive line pattern on the substrate isformed by plating a copper foil with nickel and then further plating thenickel with gold. By setting the thickness of the copper foil to 35 μmor less, a partially fine pattern with a lateral size of 50 μm or less,which is required in a flip-chip bonding process, is obtained. If such apartially fine pattern is formed, the gap between the electrodes can beshortened locally in portions to be flip-chip bonded with a largeline-and-space value maintained over the entire substrate as defined bythe pattern design rule. As a result, the conductive line pattern can bedefined efficiently and the production yield of the substratesincreases.

Also, since the conductive line pattern should be provided discretely onthe substrate, the conductive line pattern was formed by an electrolessplating technique under some conditions. In a sample, nickel was platedto a thickness of about 6 μm and gold to be plated thereon was depositedto a thickness of 0.6 μm. By plating gold to a sufficient thickness inthis manner, decrease in bond strength, which might be caused due to thefusion of gold while the LED bare chip is metal-bonded to the conductiveline pattern, can be compensated for.

Optionally, to increase the reflectivity in regions on which no LED barechips are mounted, a layer or a member, made of a material with a highreflectivity, may be provided on the conductive line pattern or on thesurface of the substrate.

On the other hand, in an LED bare chip (or element) to emit blue orgreen (or cyan) light (i.e., light with a relatively short wavelength),its multilayer structure, including the light emitting layer, isnormally provided on a sapphire substrate. The sapphire substratetransmits the blue or green light, and can be disposed at an arbitrarylocation, i.e., may be located either under or over the light-emittinglayer. Since the FC bonded structure contributes more effectively toincreasing the density, the blue-ray-emitting LED bare chips andgreen-ray-emitting LED bare chips are FC bonded on the substrate in thisembodiment. In the WB-bonded structure shown in FIG. 19( d), the n and pelectrodes are provided on the back surface of the substrate and closerto the light-emitting layer of the LED bare chip, respectively. The pelectrode is connected to the conductive line (i.e., the upper-levelconductive line) on the multilayer circuit board with a bonding wire.The n electrode is connected to the conductive line (i.e., upper-levelconductive line) on the multilayer circuit board with a conductivepaste, solder, a metal bond, or an anisotropic conductive adhesive, forexample. Optionally, an underfill material may also be used as well toconsolidate these bonds.

It should be noted that the structures and bonding methods of the LEDsto emit light rays in those colors are not limited to those exemplifiedfor the foregoing embodiment. Optionally, the LEDs on the same substratemay be all bonded by a single bonding method or by three or more bondingmethods. In any case, each of those LEDs is preferably mounted by thebest bonding technique to be selected on the specific structure of theLED. Also, to increase the reliability of bonding with the element, atleast the surface of the conductive line pattern on the substrate ispreferably a gold layer. To get the element metal-bonded with the goldlayer just as intended, the gold layer preferably has a thickness of atleast 0.5 μm, more preferably 1 μm or more.

If multiple types of LEDs are arranged on the same substrate or if theLEDs are arranged on the same substrate by multiple bonding methods, thelocation of the light-emitting layer of one LED may be different fromthat of the light-emitting layer of another LED. Accordingly, thegeometric shape (e.g., focal point or aperture ratio) of a lens to beprovided for each of those LEDs is preferably optimized according to thelocation of the light-emitting layer of the LED or the chromaticaberration to be caused depending on the color of the emission.

The layouts of the conductive lines will be described with reference toFIGS. 17 and 18.

The electrodes 80 a, 80 b, 80 c and 80 d shown in FIG. 17 are feederterminals to supply an anode potential to the four groups of LEDs toemit red, blue, green and yellow light rays, respectively. On the otherhand, the electrodes 90 a, 90 b, 90 c and 90 d are feeder terminals tosupply a cathode potential (i.e., ground potential) to the four groupsof LEDs to emit the red, blue, green and yellow light rays,respectively.

The electrodes 80 a, 80 b, 80 c and 80 d are respectively connected tothe conductive lines 81 a, 81 b, 81 c and 81 d shown in FIG. 18 by wayof via metals. On the other hand, the electrodes 90 a, 90 b, 90 c and 90d shown in FIG. 17 are respectively connected to the conductive lines 92a, 92 b, 92 c and 92 d shown in FIG. 18 by way of via metals.

A circuit that is substantially equivalent to the circuit shown in FIG.15 is realized by the multilayer structure shown in FIGS. 17 and 18.However, each of the conductive line patterns may naturally have anyother layout and is not limited to the layout shown in FIG. 17 or 18.

In this embodiment, the feeder terminals (consisting of the anode andcathode electrodes) 80 a through 80 d and 90 a through 90 d are allarranged in line in the region shown at the bottom of FIG. 17. In thismanner, the feeder terminals are collected together near one side of thesubstrate, thus making it easier to connect the card-type LEDillumination source to the connector. The ground lines can also beisolated from each other for the respective groups of LEDs to emit lightrays in multiple different colors and yet the feeder terminals can becollected together by one side of the substrate. This is because themultilayer structure described above is adopted in this embodiment.

As described above, in this embodiment, no feeder terminals are providedon the back surface of the metal plate of the card-type LED illuminationsource, and the back surface of the metal plate is flat. Accordingly, awide area of contact is ensured between this metal plate and a memberwith a good thermal conductivity (included in the illuminationapparatus). Thus, the heat can be dissipated away more efficiently fromthe card-type LED illumination source. The area of contact is preferablyequal to or greater than the area of the region in which the LEDs arearranged (i.e., the light outgoing region or LED cluster region).

In the embodiment described above, four types of LED bare chips to emitlight rays with multiple different wavelengths are arranged on the samesubstrate. However, the present invention is in no way limited to thisspecific preferred embodiment. Thus, the number of colors of theemissions (or the number of wavelength ranges to which those emissionsbelong) may be one, two or three or more than four. Alternatively, evenan LED bare chip that radiates multiple types of emissions or an LEDbare chip to emit white light by adding a phosphor thereto may also beused. It should be noted that unless an LED bare chip to emit whitelight is used, an LED bare chip normally needs to be coated with aphosphor for the purpose of emitting white light. In that case, if thephosphor is encapsulated in the space that is defined by the substrateand the reflector, the phosphor can be excited by the LED.Alternatively, a sheet on which a phosphor is dispersed may be attachedonto the upper surface of the reflector. As another alternative, thephosphor-dispersed sheet itself and the card-type LED light source maybe molded together with a transparent resin material.

Embodiment 4

Hereinafter, various specific embodiments of LED illuminationapparatuses according to the present invention will be described withreference to FIGS. 20 through 31.

First, referring to FIG. 20, illustrated is a light bulb type LEDillumination apparatus. This LED illumination apparatus basically hasthe same configuration as the LED illumination apparatus shown in FIG.3( b), but is different from the counterpart shown in FIG. 3( b) in themethod of introducing the card-type LED illumination source into theillumination apparatus. Specifically, the LED illumination apparatusshown in FIG. 20 is used as a combination of the body 96 of theillumination apparatus and a transparent housing 97. To remove thecard-type LED illumination source 95, the transparent housing 97 shouldbe temporarily taken off the body 96. A receiving portion 98, in whichthe card-type LED illumination source 96 is fitted, is provided on theupper surface of the body 96. The body 96 further includes a fixing lid99, which is used to press the upper surface of the card-type LEDillumination source 96 that has been fitted in the receiving portion 98and to fix the illumination source 96 onto the receiving portion 98. Thefixing lid 99 is supported so as to rotate (i.e., open and close) arounda shaft that is provided near one end thereof, and includes connectorelectrodes 99 a to contact with the feeder terminals 95 a on thecard-type LED illumination source 95. These connector electrodes 99 aare connected to a lighting drive circuit (not shown) that is providedinside the body 96. When combined, the fixing lid 99 and the receivingportion 98 together function as a sort of “connector”.

The fixing lid 99 has such a structure as exposing the light outgoingregion of the card-type LED illumination source 95 that is stored in thereceiving portion 98 while pressing the feeder terminals 95 a and otherportions downward. When the fixing lid 99 is closed, the back surface ofthe substrate of the card-type LED illumination source 95 thermallycontacts with the bottom of the receiving portion 98. The bottom of thereceiving portion 98 is preferably made of a material with a goodthermal conductivity (e.g., a metal material such as aluminum). Such agood thermal conductor functions as a heat sink, which can dissipate theheat that has been generated in the card-type LED illumination source 95and can prevent an excessive rise in temperature of the illuminationsource 95.

In a preferred embodiment, this illumination apparatus is constructedsuch that the transparent housing 97 can be easily removed, and thefixing lid 99 can be easily opened and closed, with the user's hands orfingers and without using any special tool. Thus, the card-type LEDillumination source 95 can be easily replaced (i.e., inserted orremoved). The transparent housing 97 may have a light diffusingproperty. Also, the transparent housing 97 may be replaced with anotherhousing 97 a that is made of a colorant, a phosphor or a phosphor.Alternatively, a lenticular lens 97 b or a light diffusing housing 97 cmay also be used. As another alternative, a double lens, a reflector, ora housing having the functions of these optical members in combinationmay also be used.

Just one card-type LED illumination source 95 is supposed to be insertedinto, or removed from, the illumination apparatus shown in FIG. 20.However, multiple card-type LED illumination sources may be insertedinto, and removed from, one illumination apparatus. FIG. 21 illustratesanother light bulb type LED illumination apparatus, in which multiplecard-type LED illumination sources are fitted. The card-type LEDillumination sources are pressed down and fixed by a pair ofopenable/closable fixing lids.

FIGS. 20 and 21 illustrate LED illumination apparatuses that can replacea light bulb type lamp. However, an LED illumination apparatus toreplace a straight-tube fluorescent lamp or a circular-tube fluorescentlamp may also be realized by using the card-type LED illuminationsources of the present invention. If an LED illumination apparatus ismade in a shape similar to the conventional straight-tube fluorescentlamp or circular-tube fluorescent lamp, then an LED illuminationapparatus according to the present invention may be used in an existentappliance in place of the conventional straight-tube or circular-tubefluorescent lamp.

FIG. 22 illustrates a desk lamp type LED illumination apparatus. Thebody 96 of the illumination apparatus shown in FIG. 22 also includes areceiving portion 98 to store the card-type LED illumination source 95therein. This receiving portion 98 includes a guide that can be used toslide and guide the card-type LED illumination source 95 thereon. Thecard-type LED illumination source 95 may be inserted into the receivingportion 98 of this illumination apparatus with its end including thefeeder terminals 95 a facing forward. When the card-type LEDillumination source 95 reaches its predetermined position, theconnection between the feeder terminals 95 a and the connectorelectrodes is complete. Once fitted, the card-type LED illuminationsource 95 is firmly fixed there due to the frictional force and will notdrop accidentally. Also, since the back surface of the substrate of thecard-type LED illumination source 95 thermally contacts with thereceiving portion 98, that contact portion is preferably made of amaterial with a good thermal conductivity.

Just one card-type LED illumination source 95 is supposed to be insertedinto, or removed from, the desk lamp type illumination apparatus shownin FIG. 22. However, multiple card-type LED illumination sources may beinserted into, and removed from, one illumination apparatus. FIG. 23illustrates another desk lamp type LED illumination apparatus, into/fromwhich two card-type LED illumination sources are inserted or removed.

FIG. 24 illustrates still another desk lamp type LED illuminationapparatus. This LED illumination apparatus adopts a connector of thetype shown in FIG. 21. That is to say, the card-type LED illuminationsources are fixed by fixing lids onto the illumination apparatus. Theuser can easily open or close these fixing lids with fingers.

FIG. 25 illustrates another LED illumination apparatus, which isportable as a flashlight or a penlight. This illumination apparatusincludes a slot 100, through which the card-type LED illumination source95 is inserted or removed. However, the card-type LED illuminationsource 95 may also be inserted or removed without using such a slot. TheLED illumination apparatus shown in FIG. 25 can operate the card-typeLED illumination source by a dry battery or a storage battery and has aportable structure.

FIG. 26 illustrates an LED illumination apparatus that can replace aconventional illumination apparatus using a straight-tube fluorescentlamp. The body 101 of this LED illumination apparatus includes aconnector, into/from which multiple card-type LED illumination sources95 can be inserted and removed. The card-type LED illumination sources95 are inserted or removed through the slot 100 of the body 101.

It should be noted that the LED illumination apparatus shown in FIG. 26is not supposed to replace a straight-tube fluorescent lamp itself but adesk lamp type illumination apparatus that uses the straight-tubefluorescent lamp.

FIG. 27 illustrates an LED illumination apparatus, which can replace aconventional illumination apparatus that uses a circular-tubefluorescent lamp. The body 102 of this LED illumination apparatusincludes a connector, into/from which multiple card-type LEDillumination sources 95 can be inserted and removed. The card-type LEDillumination sources 95 are inserted or removed through the slots 100 ofthe body 102.

FIG. 28 illustrates a downlight type LED illumination apparatus. The LEDillumination apparatus of the present invention can easily have areduced thickness, and can be easily mounted as a downlight unit on theceiling of a room or an automobile.

FIG. 29 illustrates an optical axis shifting type LED illuminationapparatus. If its portion including the card-type LED illuminationsource fitted in is rotated to an arbitrary angle around a particularaxis, the light outgoing direction can be easily changed into anydesired direction.

FIG. 30 illustrates a card-type LED illumination apparatus. A batterywith a reduced thickness such as a button battery is adopted, therebyreducing the overall thickness of the illumination apparatus itself.Such an LED illumination apparatus is thin and lightweight, and can beeasily carried about.

FIG. 31 illustrates a keychain type LED illumination apparatus. This LEDillumination apparatus is also driven by a battery with a reducedthickness such as a button battery, has reduced size and weight, andeasy to carry about conveniently.

Various specific embodiments of LED illumination apparatuses accordingto the present invention have been described with reference to FIGS. 20through 31. However, the present invention is in no way limited to thesespecific embodiments but may also be implemented in numerous other ways.

As is clear from the foregoing description of specific embodiments, ifthose illumination apparatuses are designed such that each singleillumination apparatus accepts one or multiple card-type LEDillumination sources, then card-type LED illumination sources of astandardized type are easy to popularize. For example, the illuminationapparatus shown in FIG. 21 is preferably designed so as to accept not somuch one card-type LED illumination source with a big area as multiplecard-type LED illumination sources, any of which is also insertable andremovable into/from the illumination apparatus shown in FIG. 20. In thatcase, the card-type LED illumination sources can be mass-produced andthe price of a single card-type LED illumination source can be decreasedeasily, which is one of the most important effects to achieve. Also, ifan applicable card-type LED illumination source changes with the type ofa specific illumination apparatus or the maker who produced it, suchpoor compatibility should frustrate the users. For that reason, the mainportions of the card-type LED illumination source preferably havestandardized functions or sizes.

Each of the card-type LED illumination sources according to the numerousembodiments described above uses LED bare chips that have been mountedthereon. Alternatively, a card-type LED illumination source including anorganic EL film thereon may also be used. Thus, the“insertable/removable card-type LED illumination source including LEDsthat have been mounted on one surface of a substrate” herein also refersto a card-type LED illumination source including an organic EL film on aheat-dissipating substrate.

As described above, the LED illumination apparatus of the presentinvention uses a card-type LED illumination source as an easilyinsertable/removable member, and therefore, has an extended life as anillumination apparatus and can replace any of the existent illuminationapparatuses. A card-type LED illumination source having a configurationsuch as that shown in FIG. 12 is preferably used in such an LEDillumination apparatus. However, card-type LED illumination sources foruse in the LED illumination apparatus of the present invention are in noway limited to the specific embodiments described above.

Thus, a card-type LED illumination source with any of variousconfigurations may be inserted into, and removed from, the LEDillumination apparatus of the present invention. That is to say, thepresent invention is not limited to the specific preferred embodimentsof card-type LED illumination sources that have been described abovewith reference to the accompanying drawings.

Also, the card-type LED illumination source of the present invention isapplicable for use in not just illumination apparatuses but also anyother type of apparatus. The insertable/removable card-type LEDillumination source of the present invention may be used in an appliancethat should emit as bright light as the illumination apparatus or in thelight source section of any other apparatus, for example.

It should be noted that instead of mounting LED bare chips directly ontoa substrate, LED elements (preferably of a surface bonded type),obtained by molding LED bare chips, may be bonded onto the substrate. Inthat case, the LED elements molded are fabricated separately. Thus,compared to directly mounting LED bare chips, the thermal resistancebetween the substrate and the LED bare chips increases. However, if thesubstrate has the above-described structure, even the substrate withthose LED elements mounted exhibits better heat dissipation performancethan the conventional one. Consequently, the substrate with the LEDelements integrated thereon can exhibit improved heat dissipationperformance.

INDUSTRIAL APPLICABILITY

The LED illumination apparatus and card-type LED light source of thepresent invention include: a connector to be connected to theinsertable/removable card-type LED light source; and feeder terminalsfor the light source. The LED illumination apparatus further includes alighting drive circuit. The card-type LED light source includes a metalbase substrate and multiple LEDs. The metal base surface, which is theback surface of the substrate, thermally contacts with a portion of theillumination apparatus.

In this case, a metal plate with openings, including encapsulating resinlenses and functioning as an optical reflector and a heat spreader, isdisposed on the metal base substrate. The LEDs, as well as thereflector, are encapsulated on the substrate.

Furthermore, the LED bare chips are directly bonded onto the substrate.The substrate has multiple conductive line pattern layers and also has anumber of feeder terminals along one side of one of its surfaces. Also,in a preferred embodiment, the feeder terminals have multiple groundelectrodes.

The LED illumination apparatus of the present invention uses aninsertable/removable card shaped structure as its light source portion.Thus, the heat that has been generated from respective LED elements ofthe light source can be dissipated much more smoothly. In addition, onlya light source with its life ended can be replaced with a brand-newlight source. Thus, the remaining structure of the illuminationapparatus, other than the light source, can be used for a long time.

The card-type LED illumination source of the present invention realizeshigh-density arrangement of LED elements, excellent heat dissipationperformance, and significant increase in the extraction efficiency ofthe light generated at the same time. Thus, card-type LED illuminationsources can be commercially viable products.

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. It is understood, therefore, that thisinvention is not limited to the particular embodiments disclosed, but itis intended to cover modifications within the spirit and scope of thepresent invention as defined by the appended claims.

1. An LED illumination source comprising: a metal base substrateincluding a line pattern and an insulating layer comprising a compositematerial with an inorganic filler and a resin composition, and LED barechips mounted on one surface of the metal base substrate, wherein anoptical reflector with holes to surround the LED bare chips is providedon the surface of the metal base substrate on which the LED bare chipsare mounted, and wherein stress relaxing means is provided between themetal base substrate and the optical reflector.
 2. The LED illuminationsource of claim 1, wherein a thermal resistance between the back surfaceof the metal base substrate, on which none of the LED bare chips ismounted, and the LED bare chips is 10° C./W or less.
 3. The LEDillumination source of claim 2, wherein the thermal resistance is 5°C./W or less.
 4. The LED illumination source of claim 2, wherein thethermal resistance is 2° C./W or less.
 5. The LED illumination source ofclaim 1, wherein the inorganic filler is comprises at least one materialselected from the group consisting of Al₂O₃, MgO, BN, SiO₂, SiC, Si₃N₄and AlN.
 6. The LED illumination source of claim 1, wherein the LED barechips are provided as either surface mount devices (SMDs) or chipelements.
 7. An LED illumination source comprising: a metal basesubstrate including at least one insulating layer, each layer comprisinga composite material with an inorganic filler and a resin composition,LED bare chips mounted on one surface of the metal base substrate, andat least two conductive line pattern layers stacked one upon the otherwith at least one insulating layer interposed between them, wherein theillumination source has a structure for interconnecting the at least twoconductive line pattern layers together at a predetermined position ofthe insulating layer.
 8. The LED illumination source of claim 7, whereina thermal resistance between the back surface of the metal basesubstrate, on which none of the LED bare chips is mounted, and the LEDbare chips is 10° C./W or less.
 9. The LED illumination source of claim8, wherein the thermal resistance is 5° C./W or less.
 10. The LEDillumination source of claim 8, wherein the thermal resistance is 2°C./W or less.
 11. The LED illumination source of claim 7, wherein theinorganic filler comprises at least one material selected from the groupconsisting of Al₂O₃, MgO, BN, SiO₂, SiC, Si₃N₄ and AlN.
 12. The LEDillumination source of claim 7, wherein the LED bare chips are providedas either surface mount devices (SMDs) or chip elements.